ISSN?1000-3304? CN?11-1857/O6
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¶þÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19128
[Abstract](150) [PDF 862KB](10)
Abstract:
Vanadium catalysts always show outstanding catalytic properties towards ethylene (co)polymeriztaion, while the high-valent vanadium species would be deactivated because of the generation of inactive or less active low-valent species at elevated temperature and/or in prolonged time. As proved, introducing of bulky groups into the ligands is benefit to improving the catalytic properties of vanadium complexes. Herein, in order to well control the oxidation state of vanadium species, a series of tridentate ¦Â-ketoimine type vanadium(III) complexes bearing cyclic skeleton {[(R)X(C6H4)N£½CH(C6H5)C10H7O]VCl2(THF): 2a, R = CH3, X = S; 2b, R = CF3, X = S; 2c, R = Ph, X = S; 2d, R = tBu, X = S; 2e, R = Ph2, X = P; 2f, R = Ph, X = O}, were synthesized and characterized. Because of the constrained effects of the cyclic skeleton and the stabilizing effects of the bi-chelating ring, these synthesized catalysts showed high activities and improved stabilities in ethylene (co)polymerization. In the presences of Et2AlCl and ethyl trichloroacetate, catalysts 2a ? 2f showed 8.16 ? 19.9 kgpolymer/(mmolV¡¤h), 7.68 ? 26.9 kgpolymer/(mmolV¡¤h) and 4.80 ? 42.2 kgpolymer/(mmolV¡¤h) of catalytic activities towards ethylene polymerization, ethylene/norbornene (NBE) copolymerization and ethylene/exo-1,4,4a,9,9a,10-hexahy-dro-9,10(1 ¡ä,2 ¡ä)-benzeno- 1,4-methanoanthracene (HBM) copolymerization, respectively. All of the resultant polymers exhibited a unimodal distribution, indicating that these vanadium catalysts showed single-site catalytic behaviour, even at elevated temperatures (50 ? 70 ¡ãC). Catalysts 2b, 2d, 2e and 2f showed " positive¡± comonomer effects in both ethylene/NBE copolymerization and ethylene/HBM copolymerization. Besides, 2a and 2c also exhibited " positive¡± comonomer effects in ethylene/HBM copolymerization. Cyclic olefin copolymers possessing high molecular weights (NBE: 43.1 ? 66.4 kg/mol; HBM: 90.2 ? 138 kg/mol) and high comonomer incorporations (NBE: 30.9 mol% ? 42.1 mol%; HBM: 14.7 mol% ? 25.0 mol%) were obtained facilely via direct copolymerization. The glass transition temperature is dominantly affected by the cyclic olefin incorporations and the steric hindrance of the cyclic olefin. Compared with the ethylene/NBE copolymers, the obtained ethylene/HBM copolymers showed much higher glass transition temperatures (NBE: 84 ? 105 ¡ãC versus HBM: 173 ? 188 ¡ãC).
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19093
[Abstract](198) [PDF 954KB](20)
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Polymeric hydrogels with high mechanical strength and excellent self-recovery are useful in tissue engineering, stretchable electronics and wearable devices. In this work, polyelectrolyte complexes-based hydrogels with high mechanical strength and excellent self-recovery are fabricated by complexation of poly(vinyl alcohol) modified with benzaldehyde-2,4-disulfonic acid disodium salt (BADS) (denoted as SPVA) with linear poly(ethylenimine) (LPEI) in aqueous solution followed by molding, drying and rehydration. The mechanical properties of the LPEIa/x%-SPVAb hydrogels, where x% represents the molar ratio of BADS to the monomer molar ratio of PVA, and a and b represent the feed mass ratio of LPEI to SPVA, can be well-tailored by varying the parameters such as the grafting ratio of BADS on SPVA and mass ratio of LPEI to SPVA. Stress-strain measurements indicate that the LPEI1/18%-SPVA1 hydrogels have the highest mechanical strength, with a tensile strength of ~ 10.0 MPa and a toughness of ~ 14.21 MJ/m3. A piece of the LPEI1/18%-SPVA1 hydrogel strip with a width of 2 mm and thickness of 2 mm can sequentially withstand various deformations such as bending, knotting, and twisting, and can lift a 1 kg weight without any damage. Besides the electrostatic interactions between sulfonate groups of SPVA and protonated amine groups of LPEI, Fourier transform infrared spectroscopy confirms the existence of hydrogen-bonding interactions between hydroxyl and sulfonate groups on SPVA. The synergy of strong electrostatic interactions and weak hydrogen-bonding interactions endows the hydrogels with high mechanical strength and toughness. Moreover, the hydrogels can completely recover from a strain of 200% to their original shape and mechanical properties within 1 h rest at room temperature without any external assistance. The excellent self-recovery of the LPEI1/18%-SPVA1 hydrogels originates from the high elastic retraction of polymer chains arising from electrostatic interactions and the reversibility of sacrificial hydrogen-bonding interactions. The high mechanical strength and excellent self-recovery will make the hydrogels have potential applications in aspects such as load-bearing materials, actuators and stretchable electronics.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19124
[Abstract](188) [PDF 1333KB](25)
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Eco-polymers are a kind of sustainable polymers with low environmental loads through their whole life cycles. As polymers answering the call of environment, eco-polymers were borne in 1990s while the polymer industry in the world developed very fast, now such research grows into hot point in polymer science. Employing monomers from renewable resources(not limited to renewable resources), much great progress has been made in the past three decades in China, most of them started from highly active and selective catalyst design to controllable polymerization method, till performance adjustment and functionalization, constituting a major force driving the fast development of eco-polymers in the world. In this review, we try to summarize the fundamental contributions from Chinese Scientists in eco-polymers, such as polylactic acids, polyhydroxyalkanoates, amino acid based polymers, poly(1,4-dioxan-2-one), CO2 copolymers, bio-based elastomers, 2,5-furandicarboxylic acid based polyesters, and cellulose derivatives, a perspective on their futures is provided.
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19097
[Abstract](320) [FullText HTML](203) [PDF 2418KB](34)
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Rechargeable batteries, which are among the most promising energy storage devices, have become a research hotspot related to energy-storage and energy-convert systems. While the rechargeable batteries based on liquid electrolytes commonly possess serious safety risks such as electrolyte leakage, volatilization, combustion, and explosion, polymer electrolytes display great potentials in ameliorating and addressing these problems. Conventional polymer electrolytes are generally prepared by the solution casting method, which is difficult to implement in actual production owing to its complicated operation and harsh conditions. In addition, the poor electrolyte/electrode interfacial contact in solid-state lithium batteries is also a common issue, mainly originating from the ex situ assembly technique of solid-state electrolyte. These drawbacks hinder their large-scale promotion and application. In this context have emerged the in situ generated polymer electrolytes, which aim at solving the above mentioned problems effectively. The general process of in situ preparation of the polymer electrolytes is as follows: a precursor solution consisting of monomers, lithium salts, and initiators is injected into the battery to fully wet the electrode channels and gaps, and the monomers are then polymerized in situ under certain external conditions to afford a gel/solid polymer rechargeable battery in one step. Compared to the traditional routes to polymer electrolytes, such in situ polymerization simplifies the preparation process, facilitates favorable solid electrolyte interface, and enables the electrode and electrolyte to form an integrated structure for better interfacial contact. These advantages are beneficial to an improved performance of rechargeable batteries and endow the technique with a promising application prospect. For more efficient development, it is an urgent task to review the existing process routes, reaction principles, types of polymer electrolytes, and the practical applications of in situ generated polymer electrolytes in rechargeable batteries (such as lithium, sodium, magnesium, etc.). Herein, we summarize the research progress of in situ polymerization in significantly stabilizing the electrode/electrolyte interface and inhibiting the diffusion of intermediates. Further, we discuss the challenges and development treads of in situ generated polymer electrolytes, including the prospects of quasi-solid polymer electrolytes. We believe this review paper will serve as a valuable reference and theoretical guidance for researchers engaged in polymer electrolytes.
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19050
[Abstract](347) [FullText HTML](220) [PDF 1084KB](31)
Abstract:
Compared to conventional shape memory polymers, the reversible plasticity shape memory polymers (RPSMPs) emphasize deformation and fixation at the same temperature below its transition temperature. Due to the advantages of low energy consumption and simple deformation, it has received much attention in the fields of military, aerospace and biomedicine. So it is important to understand its whole deformation process and key influencing factors. The glass transition temperature (Tg) of polynorbornene (PNB) is around room temperature, which is in favor of reversible deformation. Therefore, in this study, PNB materials with low oil filling were prepared by using PNB as the matrix and adding environmentally friendly aromatic oils with different contents. The effects of plasticizing oil content, deformation temperature and relaxation time on the reversible plasticity shape memory properties of PNB materials were studied by differential scanning calorimeter (DSC), universal electronic tensile testing machine and dynamic mechanical analysis (DMA). The results show that the plasticizing oil can continuously adjust the Tg of the PNB materials to keep it near room temperature, which is beneficial to the reversible plasticity deformation and excellent mechanical properties. When the deformation temperature is lower than the glass transition initiation temperature 2 ¡ãC, the energy consumption for material deformation is lower, and the molecular chain motion activation energy is higher, so the movement of chain segments is limited when the applied force is removed, thus, the fixation ratio is higher. The deformation temperature has little effect on the material recovery ratio. Because of the ultra-high molecular weight of PNB, when the triggering temperature is much higher than its transition temperature (Tg + 50 ¡ãC), the molecular chain entropy increases, resulting in a large entropy elastic recovery force, so the recovery ratios of all the deformed samples at different temperatures are higher than 95.0%. It is concluded that PNB has an excellent reversible plasticity shape memory performance when the deforming temperature is 2 ¡ãC lower that its onset of glass transition temperature. In addition, prolonging the relaxation time can also increase the shape fixed ratio, but the degree is limited.
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19110
[Abstract](494) [PDF 4376KB](31)
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Optoelectronic polymers possess delocalized ¦Ð electron skeletons that enable various optoelectronic properties and applications. As a frontier research directions of polymer science, optoelectronic polymers have attracted wide attention because of their fascinating properties such as low-cost synthesis, light-weight and easy manufacture of thin film devices by solution cast or printing technologies. These features have endowed optoelectronic polymers with great potential applications in the field of organic optoelectronic devices, and also have motivated chemists to construct a variety of optoelectronic polymers. This review article aims to summarize the important research progresses of optoelectronic polymers in China, including the molecular engineering, novel and controllable polymerization, regulation on properties, various aplications and theoretic studies of optoelectronic conjugated polymers.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19118
[Abstract](80) [FullText HTML](65) [PDF 2367KB](33)
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This paper made a survey on the research field of polymer physics and characterization achieved by the mainland Chinese community since reform and opening of China 40 years ago. The examples were selected for the brief introduction from three aspects: the breakthrough in concepts, the development in theories, and the innovation in techniques. It intended to highlight the creativity of modern Chinese scientists in this fundamental research field, in order to encourage young scientists to take the bigger challenges in scientific research, and to make more contributions in national economy and social development.
ÎåÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19048
[Abstract](343) [FullText HTML](205) [PDF 1474KB](5)
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Polyoxazolines have drawn much attention by researchers because of their hydrophilicity, good biocompatibility, non-toxicity. Chemical modification on polyoxazolines and their derivatives by grafting reaction with other synthetic polymer chains is one of the most important ways to improve the comprehensive properties of polyoxazoline materials. The novel amphiphilic polystyrene-g-poly(2-ethyl-2-oxazoline), PS-g-PEOX, graft copolymers were prepared through the combination of " grafting from¡± method and cationic ring-opening polymerization of 2-ethyl-2-oxazoline using the polystyrene bearing chloromethyl functional groups as the macroinitiator in the presence of activator, such as potassium iodide (KI), silver perchlorate (AgClO4) or silver trifluoromethanesulfonate (AgCF3SO3). The chemical structure and composition of PS-g-PEOX graft copolymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR). The results show that the novel amphiphilic PS-g-PEOX graft copolymers with various PEOX grafting contents ranging from 8% to 97% could be synthesized by changing the feed ratios of monomer and activator. The silver nanoparticle (5 ¨C 10 nm) content in a range from 0.1% to 3.5% was uniformly dispersed in the PS-g-PEOX graft copolymer matrix. The microphase separation of amphiphilic PS-g-PEOX graft copolymer/silver nanoparticle nanocomposite was observed and the microscopic morphology was related to PEOX contents. The hydrophilicity of the amphiphilic PS-g-PEOX graft copolymers and water contact angle (WCA) increased with PEOX content. And the WCA of PS-g-PEOX graft copolymer film with 97% PEOX content is 24¡ã. What¡¯s more, amphiphilic PS-g-PEOX graft copolymers can form stable and uniform micro/nano micelles in water. The stable oil/water suspension can be produced by adding a small amount of PS-g-PEOX graft copolymer into the incompatible water/toluene mixed system. The topological structure which formed by introducing PEOX onto PS backbones is beneficial to improve the thermal stability of PEOX. The good hydrophilicity of PEOX branches in PS-g-PEOX graft copolymer does a favor to the anti-adsorption properties against bovine serum albumin. The graft copolymer/silver nanoparticle composites behave a good antibacterial activity against E. coli, which increased with the content of nano silver.
ÎåÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19056
[Abstract](283) [FullText HTML](191) [PDF 1267KB](10)
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The copolymerization of myrcene with styrene by the half-sandwich scandium complexes (C5H5)Sc(CH2SiMe3)2(THF) (1) and (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (2) was studied. The structures and thermal properties of the obtained copolymers were characterized by NMR, GPC and DSC. The copolymerization of myrcene with styrene at room temperature had been achieved and the copolymerization activity reached up to 104 g polymer molSc¨C1 h¨C1. The myrcene-styrene copolymers with controllable compositions (myrcene content = 22 mol% ¨C 83 mol%), high molecular weight (Mn = 4.8 ¡Á 104 ¨C 11.3 ¡Á 104) and narrow molecular weight distribution (Mw/Mn = 1.49 ¨C 1.99) were conveniently obtained by changing the feed ratio of myrcene and styrene. Significant influence of catalyst structure on the stereoselectivity and comonomer distribution sequences in the resulting copolymers was observed. In the copolymerization of myrcene and styrene catalyzed by scandium complex 1, styrene started to incorporate into chains after myrene was almost completely consumed, and diblock copolymers containing cis-1,4-polymyrcene (selectivity 95%) block and atactic polystyrene block were obtained. The obtained copolymers with different myrcene contents possessed two glass transition temperatures (Tg, ¨C 63 and 96 ¡ãC), close to those of cis-1,4-polymyrcene and atactic polystyrene. In contrast, in the copolymerization of myrcene and styrene catalyzed by scandium complex 2, myrene content showed a gradient decline accompanied by styrene content increasing gradually, producing gradient copolymers containing 3,4-polymyrcene (3,4-selectivity 75%, cis-1,4-selectivity 25%) and syndiotactic polystyrene. The obtained copolymers with different myrcene contents possessed a Tg at ¨C35 ¡ãC and a melting temperature (Tm) at 254 ¡ãC, originating from polymyrcene block and syndiotactic polystyrene block, respectively. There is a great difference in the reactivity ratios between myrcene and styrene in the copolymerization catalyzed by scandium 1 (rMy >> rSt). However, the gap between the reactivity ratios of myrcene and styrene in the copolymerization catalyzed by scandium complex 2 was much smaller (rMy = 8.47, rSt = 0.76) and gradient copolymers were generated.
ÎåÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19049
[Abstract](223) [FullText HTML](150) [PDF 1252KB](12)
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Combining the advantages of information encoding and function realization, DNA-conjugated nanomaterials have attracted great attention recently. As a typical anisotropic material, gold nano-triangle is of great value due to the sharp vertices. However, the yield of nano-triange is not high through current wet synthesis. In order to solve this problem, we propose a new strategy of shape selective separation of gold nano-triangles with the assist of thiol-DNA. The attachment of DNA to the surface of gold nanoparticles, on one hand, can stabilize the nanoparticles by shielding the direct contact between gold nanoparticles and solution environment. On the other hand, according to the particle shape, size and the surface charge density, gold nanoparticles have different mobilities in the electric field. As a result, gold nanoparticles can be separated by gel electrophoresis. The DNA-assist purification method gives a yield of above 80% of gold nano-triangles, which is also universal for the separation of nano-triangles with different sizes. More importantly, the surface-modified DNA can simultaneously separate and encode gold nano-triangles. By rational designing the DNA sequence, nano-triangles can be assembled on DNA origami and higher-order structures can be constructed.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19100
[Abstract](439) [FullText HTML](199) [PDF 2413KB](57)
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Polymer semiconductors have attracted substantial interests in both academia and industry, recently, attributed to their distinctive advantages, including widely-tunable chemical structure and optoelectronic property, solution processability, and mechanical flexibility. In the last decade, a great deal of efforts have been dedicated to developing P-type (hole transporting) polymer semiconductors, however the development of N-type (electron transporting) polymer analogues lags far behind compared to their P-type counterparts due to the scarcity of highly electron-deficient building blocks, accompanied steric hindrance, and synthetic barriers. In fact, high-performance N-type polymer semiconductors are essential for organic complementary logic circuits and p-n junctions, hence it is imperative to develop high-performance N-type polymer semiconductors, which hinge on the design and synthesis of new electron deficient building blocks with compact geometry and good solubilizing capability. Among various electron deficient building blocks, imide-functionalized (hetero)arenes hold the most promising structural and electronic features for enabling N-type polymer semiconductors. This account summarizes the latest progress of N-type polymers, particularly the polymers based on imide-functionalized (hetero)arenes developed by our group. These new imide-functionalized (hetero)arenes include a series of ring-fused ladder-type heteroarenes up to 5 imide groups and 15 rings in a row, which offer a remarkable platform for developing N-type polymer semiconductors with widely tunable optoelectronic property and film morphology. In addition, a series of ¦Â-position functionalized or modified bithiophene imide derivatives are also devised and synthesized. The introduction of the most electronegative fluorine atom and the substitution of thiophene with more electron deficient thiazole yield further lower-lying LUMO energy levels, which promote N-type characteristics for the polymer semiconductors in devices. This account introduces the materials design principles for N-type polymer semiconductors and elaborate the synthetic routes to the new imides and the corresponding polymer semiconductors. In addition, the N-type device performance of the polymer semiconductors based on these imide-functionalized building blocks in organic field-effect transistors (OFETs) and polymer solar cells (PSCs) are commented, and the materials structure-property correlations are elaborated. Finally, our insights into future materials innovation of N-type polymer semiconductors by inventing new imide-functionalized building blocks are provided.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19085
[Abstract](273) [FullText HTML](189) [PDF 2729KB](28)
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Under healthy conditions, cells/tissues can function normally in their natural microenvironment due to the large amount of biomolecules herein. However, the normal cell/tissue microenvironment will be disrupted after certain pathological events due to the loss and damage associated with certain biological entities, and the disrupted microenvironment is usually accompanied by abnormal biological signals. Therefore, when designing biomaterials , one of the primary considerations is to restore the healthy cell/tissue microenvironment at the tissue-biomaterial interface and reconstruct the original biological structures in situ by mimicking human tissues, which is of critical importance to the total repair of the disease site. However, most of the existing biomaterials are biologically inert and lack interaction with the host. To improve the biocompatibility and biofunctionality of the substrate materials and to enhance their biomimeticity, the surface modification technology has gained increasing interest in recent decades. The rational modification of the tissue-biomaterial interface can improve beneficial interaction between the substrate material, while still preserving the physical properties of the material that are favorable for certain applications. Based on our previous study on cell/tissue biological and pathological environment, our group has carried out a lot research on the development of new biofunctional interfaces using polymer-based ligands or functional moieties, of which properties could be tailored according to the specific characteristics of particular microenvironment. The as-developed biomaterials could fulfill a variety of roles including osteogenic promotion, gene transfection, antibacterial and antitumor applications. It was also confirmed that these polymer-modified materials can autonomously interact with the biological tissues and execute the designed biological functions in a highly responsive manner. With the advances in synthesis chemistry and processing technology, new biomimetic materials with better fineness and structural precision will attract greater interest in related areas. In this paper, we will summarize the relevant research work in recent years and discuss those existing challenges.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19051
[Abstract](766) [FullText HTML](204) [PDF 3385KB](15)
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The self-assembly of symmetric ABA tri-block copolymers inside an oil-in-water emulsion droplet upon solvent evaporation is investigated by Monte Carlo simulations, and the simulation results are compared with those in AB di-block copolymer systems. A morphological phase diagram is constructed in the two-dimensional space composed of surfactant concentration (¦Õ) and the volume fraction of B segments (fB). Non-porosity particles, closed-porosity particles, open-porosity particles, capsules, and micelles are observed. The study shows that when fB ¡Ü 1/2, the increase of ¦Õ leads to a morphological evolution from non-porosity particle to closed-porosity particle and open-porosity particle, while for fB > 1/2, micelles are observed in a larger ¦Õ window. The fraction of bridge chains (vB) as a function of ¦Õ is always much lower than the corresponding bulk value. Moreover, the mean-square radius of gyration (<Rg2>) of the ABA tri-block copolymer chains is much smaller than that of the corresponding AB di-block copolymer chains with the same fB and ¦Õ values under the same condition. Due to the influence of chain conformation, no capsule appears in the ABA tri-block copolymer system when fB ¡Ü 1/2, which is different from the case of the corresponding AB di-block copolymer system. The specific surface area of particles with the same morphology falls into almost the same p regime, which indicates that the particle morphology largely determines its specific surface area. By calculating the formation energy of particles, it is confirmed that the surfactants in the system are the key to the formation of porous particles. All these are the same as what have been observed in AB di-block copolymer systems. In addition, the radial density distributions of water molecules in ABA tri-block system and the corresponding AB di-block system are not exactly the same, but the particle sizes are basically identical. The evolution processes including the typical non-porosity particles, closed-porosity particles, and open-porosity particles, as well as the bridging fraction during solvent evaporation are further discussed.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19052
[Abstract](289) [FullText HTML](181) [PDF 927KB](20)
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Azobenzene (Azo) can absorb specific wavelength light that makes a change from trans-state to cis-state structure. Energy storage can be achieved by the difference in energy levels between the two isomers, so Azo is often used as energy storage materials. The conventional Azo photo-thermal storage materials have problems of relying on the utilization of ultraviolet light, requiring a high temperature stimulation, and a low-rate heat release. Herein, by utilizing diazonium salt method to introduce thiazole and methoxy groups into Azo to form a push-pull electronic structure, thiazole-heterocyclic Azo (t-Azo-h) achieves fast heat release. The photo-thermal storage composite (t-Azo-h/rGO) is obtained through grafting azo monomers onto the surface of reduced graphene oxide (rGO). Due to the close accumulation of Azo units on the surface of rGO, t-Azo-h/rGO of graphene-templated assembly increases the intermolecular interaction, resulting in an energy storage density of 89 Wh/kg, a half-life of 10 h, and a high power density of 890 W/kg at a heating rate of 5 ¡ãC/min. UV spectrum shows the maximum absorption intensity is at 435 nm, realizing absorption of the violet region because of molecular polarizability increased due to push-pull electronic properties. Red shift of spectral absorption broadens the use of sunlight. Owing to fast heat release, t-Azo-h/rGO reaches the temperature difference of 2.6 ¡ãC under 60 ¡ãC and 3.8 ¡ãC under 80 ¡ãC, respectively. By designing thermochromic pigment in combination with photo-thermal film, the decoloration occurs in two thermochromic pigments (red ¡ú colorless at 62 ¡ãC, blue ¡ú colorless at 82 ¡ãC) due to the heat release of photo-thermal material under heat stimulation. The t-Azo-h/rGO with fast heat release achieves the thermal visualization by optimizing stimulus. By designing push-pull electronic structure, a kind of photo-thermal material with fast thermal output is obtained and photo-thermal material with rapid heat release could finish a higher power density output at low temperature than that of slow heat release. At last, the thermal display with temperature response is realized by combining thermochromic pigments. Thermal display is expected to be applied in temperature supervisory and information encryption field.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19047
[Abstract](399) [FullText HTML](244) [PDF 1110KB](43)
Abstract:
The fabrication of conductive hydrogels with electric-induced self-healing capability exhibits great significance to the development of safe and long-life electronic devices, expanding their application in the field of flexible electronics. For this purpose, the conductive, self-healing nanocomposite hydrogel was fabricated via in situ free radical polymerization with modified Au nanoparticles (NPs) as crosslinkers, poly(o-phenylenediamine) (PoPD) nanobelts as conductive additives and N-isopropyl acrylamide as monomer in the presence of initiator and catalyst. Before the polymerization, N,N-bis(acryloyl)cystamine (BACA) with vinyl groups in the molecular structure was introduced on the surface of Au NPs through the interaction of thiolate-Au (RS-Au) bonding. The successful binding behavior between Au NPs and BACA was confirmed by the transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The PoPD nanobelts with a length of nearly 100 ¦Ìm and a diameter of 200 nm were prepared by mixing HAuCl4 and oPD solution, and further stirring it at room temperature. The conductivity of PoPD nanobelts could be greatly improved through the strategy of chemical doping by introducing Fe3+ into the aqueous solution. For example, the conductivity can be obtained as high as 5.5 S/m when the concentration of Fe3+ employed was 1 mol/L. By combining the obtained hydrogel network with uniform and compact polymer network, the produced hydrogel showed excellent stretchability (larger than 2400%) and mechanical strength (larger than 1.2 MPa). Impressively, motivated by the thermal instability and Joule's first law, the damaged hydrogel exhibited rapid and highly efficient self-healing performance when the external power supply was available, because of the heating power generated by hydrogels at the cracks. For example, by the aid of power supply with the electric current of 0.05 A, the damaged hydrogel could be healed in 15 min with the optimal healing efficiency of nearly 90%. This prominent performance would contribute greatly to the exploration of flexible electric devices with excellent real-time self-heal ability under the working state from functional hydrogels.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304
[Abstract](81) [PDF 0KB](0)
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We designed and synthetized a new non fullerene acceptor with an A-D-A strucutre, named IDTO2HT-2F, based on indacenobis(dithieno[3,2-b:2¡ä,3¡ä-d]pyran) for organic solar cells. The dithieno[3,2-b:2¡ä,3¡ä-d]pyran will improve the electron-donating capability of the unit and lift the highest occupied molecular orbital (HOMO). Thus, the band gap decreases, which makes the maximum absorption peak red-shift. Theoretical calculation based on density functional theory(DFT) proved the feasibility of this molecular design. The molecule IDTO2HT-2F has a narrow bang gap of 1.30 eV with the solid absorption edge extended to 956 nm, which is complementary to that of the polymer PM6 film. The broad absorption of the active layer ensures the photovoltaic device to produce high photocurrent. With 0.5% DIO additive and thermal annealing 120 ¡ãC for 10 minuntes, the organic solar cell based on the acceptor IDTO2HT-2F and the polymer PM6 exhibits a power conversion efficiency (PCE) of 10.85% with a short circuit current density (Jsc) of 20.61 mA cm?2, a open-circuit voltage (Voc) of 0.86 V and a fill factor (FF) of 0.62. The results indicate that the strategy of introducing pyran into the molecular backbone is an effective way to tune the absorpion and energy level of the molecules, which is also a promisng method to design new non fullerene acceptors.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19099
[Abstract](193) [PDF 879KB](8)
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A kind of representative poly(amide-imide) (PAI) films derived from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and amide-containing diamine i.e. N,N'-(1,4-phenylene)bis(4-aminobenzamide) (PABA) were prepared via thermal imidization, and then annealed at various high temperatures including 350, 375, 400 and 425 ¡ãC, respectively. With the increase of annealing temperature, the heat-resistance of PAI films were improved with higher Tg values, whereas their thermal decomposition stabilities were reduced to some extent especially when annealed above 400 ¡ãC. All of these PAI films exhibited ultralow thermal expansion with negative coefficient of thermal expansion (CTE) values from ¨C6.87 ppm/¡ãC to ¨C3.84 ppm/¡ãC even in a wide temperature range of 30 ¨C 400 ¡ãC. It was noted that the CTE values of PAI films were increased to around zero as annealing temperature elevated. The annealing effect on aggregation structures and thermal expansion behavior was further investigated by birefringence (¦¤n), FTIR, WAXRD and WAXS. The birefringence of PAI films was extraordinarily larger than that of aromatic polyimide films, indicating that PAI molecular chains were more oriented in the in-plane direction. Their ¦¤n values ranged from 0.2438 to 0.2621 as annealing temperature increased from 350 ¡ãC to 425 ¡ãC. The hydrogen bonding interactions were proved to be maintained even at high temperature as the main reason for the dimension stabilities of PAI films. It was also found that annealing at high temperature could contribute to the enhanced intermolecular interactions. In addition, the intermolecular chain distance of PAI films was observed to be reduced with the increasing temperature, suggesting that molecular chains were packed more densely. Furthermore, the interchain distance in the film thickness direction was more affected by annealing with large variation than that of in-plane direction. PAI-425 film showed significantly negative thermal expansion mainly because of its expanding out-of-plane interchain distance. Based on high temperature annealing, the relationship between thermal expansion behavior and aggregation structures of PAI films was established to be used for the regulation and control of thermal expansion. It provided a new strategy to prepare heat-resistant polymer films with ultralow CTE values by the structure design and high temperature annealing.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19107
[Abstract](136) [PDF 0KB](2)
Abstract:
Polymer translocation through a nanopore is of ubiquitous importance in many biological processes such as DNA and mRNA translocation through nuclear pores, protein transport across membrane channels. In real systems, polymer translocation process usually involves complex environments. One typical example is there present different environments inside and outside the nanopore. It is interesting to study polymer translocation in an asymmetric environment. Here, Langevin dynamics simulation is performed to study polymer translocation through nanopore in an asymmetry bath of active particles and passive particles. The polymer is modeled by a bead-spring chain and the active particle is modeled by active Brownian particles with inherent orientation. We find that with the increasing of the particle activity, the translocation probability of polymer chain toward active bath increases quickly, finally reaches a saturation value. This may be because active particles exert a drag force on the polymer chain. Additionally, as the bath activity increases, the mean translocation time of polymer chain decreases fast and then increases slightly. The physical mechanism of the non-monotonic change is that the increase of the bath activity will induce the increase of tension in polymer chain, which results in a drag force toward active region. However, when the bath activity is large enough, crystalline layers of active particles are formed near the boundary, which inhibits the motion of active particles and increases translocation time of the chain. Furthermore, we find that the profile of translocation time at small active force can be fitted by log-normal distribution. Moreover, we also pay attention to the length effect of polymer chain on translocation mechanism at moderate active forces. The longer polymer chain and the higher activity of particles can lead to a larger value of drag force on the polymer chain. Our results may provide an insight into the translocation behavior of polymer chain, and help us understand the non-equilibrium processes in living organisms.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19094
[Abstract](110) [PDF 1150KB](8)
Abstract:
Cascade polymerization, or domino polymerization, is a polymerization process involving two or more consecutive polymerizations under the same reaction condition, in which the subsequent polymerizations result as a consequence of the functional polymer intermediates formed in the previous polymerization step, i.e., two or more polymerizations proceed cascade in an in situ one feeding step, one pot system. As the separation and purification of intermediate polymers are not needed, cascade polymerization has the characteristics of " green¡± and high efficiency, which is especially important in the synthesis of block copolymers. This review introduces the concept of cascade polymerization, with the focus on the cascade polycondensation-coupling ring-opening polymerization (PROP) method developed by our research group, as well as the kinetics, thermodynamics and the application of PROP in the synthesis of polyesters and copolyesters. By the combination of chain-growth and step-growth polymerization together in one system, PROP has the merits of fast polymerization speed, easy to handle with mild polymerization conditions, controlled rigid to soft segments weight ratio, and can be used for the synthesis of multiblock copolymers which are hard to be synthesized by traditional polymerization techniques. These multiblock copolyesters have potential applications in elastomers and energy storage materials.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19108
[Abstract](164) [PDF 0KB](1)
Abstract:
A La-based metal organic framework (La-BDC) was synthesized by a solvothermal method and then compounded with polycarbonate (PC) to prepare PC/La-BDC composites. The experimental (TGA, cone, Vertical burning test, etc.) results showed that La-BDC improved the fire safty and thermal stability of PC. Compared with the neat PC, 2 wt% La-BDC could increase the two maximum decomposition temperatures (Tmax1 and Tamx2) of PC in air atmosphere by 43 and 40 ¡ãC, respectively; 4 wt% La-BDC could reduce the values of peak heat release rate (PHRR) and average specific extinction area (ASEA) by 50% and 38%, respectively. PC/LaD-4 composites reached UL-94 V-0 rating in vertical burning test. On the one hand, naked La metal ion cluster, as a coordinated center, afforded La-BDC activity in catalytic oxidation, isomerization reactions etc., imparting it the ability to catalyze char formation (cross-linking) in the combustion and degradation process of PC matrix. From SEM images and Raman spectrum, the denser and highly graphitized char layers were obtained. The char layers reduced the contact between the matrix and oxygen, effectively suppressing the spillover of heat, pyrolysis products and toxic fumes. On the other hand, the rod-like crystal structure of La-BDC and the mesopores contained in its own framework structure made it play a role in adsorption and retarded of smoke generation.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19132
[Abstract](113) [PDF 0KB](1)
Abstract:
Based on the analysis of uniaxial stress-strain curves, a set of important mechanical properties of elastomer materials can be determined. To unveil the physics behind stress-strain curves, along a century research history, more than 30 constitutive models have been developed. These constitutive models are important contents in continuity mechanics and statistical mechanics. Unfortunately, owe to their complexity in the physical setting and the computing of models, select an apposite model and proper ranges of parameters to make reliable interpretation is difficult. But it is extremely important in the conduction of computer simulation to explore a real material. Here, we summarized the fundamental assumptions, boundary conditions, general ranges for model parameters and the characteristics of stress-strain curves of these typical models. Equations associated with phenomenological models, statistical mechanics models and their deviations were listed. Through the analysis of the best fitting of these modeling stress-strain curves using the coefficient of determination and Fr¨¦chet distance, the similarity and mathematically equivalence of models were quantified. It was found that Gent model and Warner model, Three-Chain model and Eight-Chain model have mutual equivalence in the depiction of stress-strain curves with strain hardening. Other models can un-directionally replace some models with less parameters and computational complexity. This work can help the selection of the proper constitutive models to simulate complex stress-strain behaviors of elastomer materials. It also may benefit the development of advanced elastomer materials and the application of theoretical models, for the mutual promotion of fundamentally theoretical research and cutting-edge elastomeric material development.
Ò»Ð£ ,?doi: 10.11777/j.issn1000-3304.2019.19115
[Abstract](136) [PDF 1987KB](10)
Abstract:
Heterophasic copolymerization of propylene based on MgCl2-supported Ziegler-Natta catalysts, that is, sequential propylene homopolymerization or copolymerization with minor amount of ethylene followed by ethylene/propylene random copolymerization for EPR, is a major polymerization technique in polypropylene industry, whose products, depending on their EPR contents, include high impact PP (hiPP, where EPR weight fraction is normally less than 40%) and thermophastic olefin elastomer (TPO, where EPR weight fraction is higher than 50 wt%). Compared to hiPP, the production of TPO is rather more challenging, for increased EPR contents makes it very difficult to prevent EPR from overflowing to the polymer particle surfaces, which will mess up with the particle morphology and lead to serious reactor fouling issues perturbating the production continuity. How to control the particle morphology at increased EPR contents with EPR being authentically contained inside without contaminating the surfaces has become a key scientific issue in the way of further developing heterophasic copolymerization of propylene to TPO. This paper reports that the solution may lie in a simultaneous croos-linking of EPR using nonconjugated ¦Á,¦Ø-diolefin during its polymerization. It is shown that simultaneous cross-linking to a great exten alters EPR¡¯s viscoleastic properties, exponentially increasing its low-shear viscosity and elasticity. As a result, EPR no longer poses as aggregated volatile droplets which after cogulation by hot-compression agglomerate to large-size phase domains; instead, it features dispersed particles discrete to each other. In turn, no overflowing of EPR occurs to the polymer particle surfaces. This research provides a solution to heterophasic copolymerization of propylene to high EPR content polypropylene thermoplastic elastomer.
ÁùÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19109
[Abstract](664) [FullText HTML](1395) [PDF 1695KB](110)
Abstract:
The interplay between polymer science and supramolecular chemistry leads to formation of various polymeric supramolecular systems. Polymeric supramolecular systems may be of abundant supramolecular structures, thus endowed with many fascinating properties and functions such as reversibility, adaptiveness, self-healing, and stimuli-responsiveness owing to the dynamic nature of noncovalent interactions. This review is aimed to summarize some research progresses on polymeric supramolecular systems in China, including mesogen-jacketed liquid crystalline polymers, non-covalent connected micelles, supramolecular self-assemblies from amphiphilic hyperbranched polymers, layer-by-layer assemblies, supramolecular polymers from controllable fabrication, and artificial molecular chaperones from controllable assembly.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19086
[Abstract](360) [FullText HTML](246) [PDF 1109KB](40)
Abstract:
Surface deposition systems such as dopamine and tannic acid have received great attention in recent years and have been widely applied in surface modification of polymer separation membranes. It is generally accepted that only polyphenols containing catechol structure can effectively form surface coatings. This paper reports a novel surface co-deposition systems based on ferulic acid and Cu2+. It should be noted that ferulic acid, a monophenol, contains only one phenolic hydroxyl group, without acatechol structure. Co-deposition coatings were prepared on various substrates, and the effects of composition and deposition time were investigated. Results indicate that the ferulic acid/Cu2+ system is able to form coating layer on most substrates. However, the coatings cannot be effectively formed on highly hydrophilic susbtrates such as silica, glass, and quartz. Microporous polypropylene membrane with surface coatings was prepared under optimal deposition conditions, and the surface structure and properties were characterized by field emission scanning electron microscopy (FE-SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), zeta potential analyzer, and water contact angle measurement. The modified membranes were applied to the separation of oil-in-water emulsions and dye adsorption. The results show that the modified membrane becomes hydrophilic and strongly negatively charged, while the surface porous structure changes little. The modified membranes can be used for the separation of various oil-in-water emulsions with high separation efficiency. It is also demonstrated that the membranes can be used repeatedly in the separation of emulsions. Furthermore, the coatings endow the membranes with strongly negatively charged surfaces, and hence the modified membranes show great potential in the adsorption of positively charged dyes. The results may introduce a novel monophenol-based system for surface deposition and greatly expand the types of surface deposition phenols.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19064
[Abstract](316) [FullText HTML](202) [PDF 1112KB](39)
Abstract:
It is a traditional method to improve the thermal conductivity of matrix by adding fillers. However, it is a great challenge to construct a dense heat conduction network in composite material. The current researches on building thermal conductive network is to combine different fillers through structure design for achieving high thermal conductivity with the lowest possible filler content. Due to the electrical insulation requirements of electronic equipment, hexagonal boron nitride (h-BN) has been extensively studied as an inorganic thermal conductive filler. It has a layer structure that shows a relatively high TC of 300 W¡¤m¨C1¡¤K¨C1 in the h-BN planar direction. In this study, the foam was introduced into the epoxy resin as a skeleton, and thermal conductive network was constructed by immersing the BN/E51 mixture into the foam. By comparing the hot deformation behavior of two kinds of foams with different structures and compositions: polyurethane foam (PF) and nano-melamine (melamine) foam (MF), epoxy resin-based composites with high thermal conductivity were obtained by hot press curing under the right compression ratio. PF has a large single arm size and good elastic deformation ability, but it is easy to become a barrier between BN, which is bad for forming thermal conductive path after compression. However, MF has a small single arm size and can be broken into four needle-like scaffold structures after compression. The needle-like scaffold structure promotes the good dispersion of BN, and finally forms a thermal path of BN throughout the material, which plays a key role in improving the thermal conductivity of the composite. As a result, MF-BN/E51 showed an excellent thermal conductivity of 3.88 W¡¤m¨C1¡¤K¨C1 at 41 wt% BN load when the degree of hot pressing was 90%. It provides a new way for the composites to achieve a higher thermal conductivity with a less filler load.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19078
[Abstract](361) [FullText HTML](224) [PDF 1558KB](18)
Abstract:
This study discusses a new strategy for synthesis of long chain-branched polypropylene (LCB-PP) with Ziegler-Natta catalysts, which, on the basis of conventional nonconjugated ¦Á,¦Ø-diolefin/propylene copolymerization incapable of affording LCB, utilizes a dichlorosilane-functionalized ¦Á,¦Ø-diolefin instead to carry out the copolymerization. Such a copolymerization with Ziegler-Natta catalysts will give PP bearing pending dichlorosilane functional groups, and it will undergo facile interchain condensations, leading to long chain-branched formation under methanol treatment and water vapor treatment. A MgCl2/TiCl4 catalyst containing a diether-type internal electron donor, 9,9-bis(methoxymethyl)fluorine (BMMF), was employed to catalyze di(5-hexenyl)dichlorosilane/propylene copolymerization in slurry conditions. It was found that di(5-hexenyl)dichlorosilane neither did harm to catalyst activity, nor changed the chain transfer/chain termination reaction of the original propylene polymerization. Incorporations of the mono-polymerized di(5-hexenyl)dichlorosilane were found to be between 0.02 mol% and 0.1 mol%. After the copolymerization completed, the obtained copolymers were treated with methanol or water vapor, respectively. Both the treatments could effectively transform the polymer chains-pending dichlorosilane groups into siloxane groups. The condensation degrees were distributed, which were centralized between 2 and 3 with methanol treatment. Water vapor treatment showed higher efficiency for dichlorosilane condensation than methanol treatment did. It could be found that water-treated samples exhibited systematically higher degrees of long chain-branched than their methanol-treated counterparts did with multiple evidences. Gel permeation chromatography measurement showed that the molecular weights of the copolymerized samples treated by both water vapor and methanol were improved, and the copolymers treated by water vapor in the Mark-Houwink equation curve were more deviated from the linear polypropylene than those of methanol treatment. The linear viscoelasticity of copolymers with different di(5-hexenyl)dichlorosilane concentrations after water vapor treatment and methanol treatment was investigated by means of small amplitude oscillatory shear (SAOS) to verify the existence of long chain-branched structure. According to extensional rheometry measurement, the strain hardening phenomena of the copolymers treated with water vapor were more obvious than those treated with methanol.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19074
[Abstract](231) [FullText HTML](141) [PDF 1143KB](9)
Abstract:
The dynamical and conformational properties of individual ring polymers with different chain lengths are investigated in Poiseuille flow through a tube using a hybrid mesoscale hydrodynamic simulation method, and migration behaviors are compared with those of linear chains. As the flow strength is increased, the ring chains migrate towards the centerline of the tube when the hydrodynamic interactions are included, but towards the tube wall when the hydrodynamic interactions are switched off. By analyzing the radial center-of-mass distribution function and the width of the distribution function of the ring chains, our studies reveal that the migration towards the centerline of the tube should be attributed to the hydrodynamic interactions rather than to the shear gradient in the Poiseuille flow. With the increase of flow intensity, the ring chains stretched more along the flow direction and shrunk smaller along the radial direction, independent of the location of their center-of-mass across the tube. When the hydrodynamic interactions are switched off, the extension along the flow direction and the shrinkage along the radial direction of the ring polymers are more pronounced than those with the hydrodynamic interactions. For a given flow strength, the longer the ring chain is, the eaiser it is to concentrate around the center of the tube due to the stronger hydrodynamic interactions between the chain and the tube wall, and the resulting distribution structure transits from the platform to the bimodal, and finally to the single-peaked with increasing chain length. By comparing the center-of-mass distributions and the structural properties between the ring and linear chains with the same chain length or the equilibrium radius of gyration, our simulation results show that the linear chains exhibit a more stretched conformation along the flow direction than the ring polymer chains, leading to the outward migration with a lower number density in the tube center.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19092
[Abstract](351) [FullText HTML](221) [PDF 1087KB](22)
Abstract:
The poor film-formation ability of azobenzene carbon thermal storage materials with graphene as templates limits their practical application due to the rigid structure of graphene sp2 hybridization. In this study, we addressed this issue by employing polynorbornene as the templelate given that polymers much outperform graphene in terms of film formation, flexibility, and self-supporting property. Herein, azobenzene attached with two methoxy and two carboxyl groups was firstly synthesized to regulate the photoisomerization and energy density. Next, polynorbornene (PNB) templates with various molecular weights were prepared by ring-opening metathesis polymerization (ROMP) with different molar ratios between monomer and catalyst. Azobenzene was then grafted onto the side chain of PNB through amidation reaction to afford azobenzene-grafted polynorbornenes with diverse grafting densities. Experimental results showed that with the increasing molecular weight of PNB template, the graft density of azobenzene rose first but subsequently fell. As for the film formation ability, PNB-Azo-500 with the highest graft density (36%) could hardly form an intact film, while PNB-Azo-900 exhibited the best film formation ability despite a slightly lower graft density (31%). Therefore, PNB-Azo-900 was involved in the following measurements. Tensile testing indicated that the PNB-Azo-900 film possessed good flexibility and self-supporting behavior by achieving a strain of 120% and a tensile strength of 21.5 MPa. Photoisomerization and energy density was characterized by UV-absorption spectroscopy and differential scanning calorimetry, respectively, which suggested that the film effectuated energy storage under 365 nm UV-light irradiation and the energy density reached 34 Wh/kg. The stored energy could be released as heat when the film was expoed to 550 nm green light or heat source stimulation, during which the highest temperature was 1.25 ¡ãC. Such excellent energy storage and light responsiveness endowed this PBN film with potential applications in the field of space thermal management.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19070
[Abstract](373) [FullText HTML](251) [PDF 964KB](23)
Abstract:
Block copolymer (BCP) nanoparticles with three different block sequences, PDMA-PNAT-PDAAM (M-N-D), PDMA-PDAAM-PNAT (M-D-N) and PDMA-P(NAT-co-DAAM) (M-[N-co-D]), are prepared via polymerization-induced self-assembly (PISA). Soluble N-acryloyloxy thiomorpholine (NAT) and diacetone acrylamide (DAAM) are used as monomers to form insoluble core blocks in water, while PDMA35 bearing a trithiocarbonate is utilized as stabilizer and macromolecular chain transfer agent (macro-CTA) to render a RAFT control. Specifically, M-[N-co-D] nano-objects are synthesized via direct RAFT dispersion copolymerization of NAT and DAAM at 70 ¡ãC employing PDMA35 macro-CTA. To produce M-N-D and M-D-N triblock copolymers, PDMA-PNAT (M-N) and PDMA-PDAAM (M-D) nano-objects are prepared via RAFT dispersion PISA syntheses of NAT and DAAM respectively utilizing PDMA35 macro-CTA and then used for seeded dispersion polymerization of DAAM and NAT respectively without intermediate postpolymerization purification. The thioether moiety in NAT can be oxidized by reactive oxygen species (ROS) into a hydrophilic sulfoxide. Therefore, in the precense of hydrogen peroxide (H2O2), oxidation-responsive morphological degradation of these nano-objects occurs due to the increasing hydrophilicity of NAT units. Given the poor control over polymerization of NAT in pure water, 1,4-dioxane is used as a cosolvent to the PNAT block. So the PISA syntheses are conducted in water/1,4-dioxane (9/1, V/V) mixture to achieve a good control over the molecular weight and narrow distribution. 1H-NMR spectra indicate that quantitative monomer conversions (> 99%) are achieved within 5 h. Differential scanning calorimeter (DLS) and transmission electron microscopy (TEM) are used to characterize final morphologies of PISA-generated nano-objects and morphological evolution of nano-objects in the presence of H2O2 (10 mol/L). These aqueous sequence-controlled PISA formulations are expected to provide responsive nanoparticles with tunable kinetics due to the response-dependent morphological transitions, which may be potentially used as carriers for drug delivery and controlled release.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19072
[Abstract](340) [FullText HTML](212) [PDF 1148KB](18)
Abstract:
The phase behavior of diblock copolymer AB/homopolymer C blends in solution was studied by simulated annealing method. The study was focused on the compatibilization between the homopolymer and the copolymer with repulsive interactions due to the addition of solvent. We investigated the amount of solvent (characterized by the concentration of the polymer segments ¦µ), the volume fraction fc of the homopolymer C, the ratio of homopolymer chain length to the copolymer chain length X, the repulsion between C and A or B segments, ¦ÅAC and ¦ÅBC, and the attraction between solvent and C on the phase behavior of the blending system. We built phase diagrams in the space of ¦µ and fc at different X. Studies have shown that when X is less than 0.5, and the values of ¦ÅAC and ¦ÅBC are not very large, the addition of solvent strongly selective to A and C segments can improve the compatibility of the system. In solution, lamellae, gyroids, cylinders in layers, core-shell cylinders and cylindrical structures are formed. Moreover, the structure of cylinders in layers has not been observed in the neat diblock copolymer system. C-segments are distributed at the interfaces between A/B domains at high ¦µ region, while they are inside the A domain at low ¦µ region. Short homopolymer chains are easily compatible with diblock copolymers. Macroscopic phase separation has taken place in long homopolymer chains even with a small amount of homopolymer added. Moreover, increasing the values of ¦ÅAC and ¦ÅBC will reduce the compatibility of the system. The transformation between different phases and that from microphase separation to macrophase separation are the results of the competition between the energy and entropy of the system. The macrophase separation in the solution system is different from that in the melt system. Some C-segments are at the interface of AB domains to reduce the contact between A and B segments in the solution system, while all C-segments are separated from the AB domains in the melts.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19111
[Abstract](258) [FullText HTML](147) [PDF 1151KB](7)
Abstract:
To realize the intelligent precision manufacturing of oscillating packing injection molding (OPIM), the whole process of OPIM was creatively simulated by computer-aided technology, Moldflow. In the process of simulation, the model was built as a dumbbell-shaped tensile spline and the complex dynamic fluctuating flow field caused by reciprocating piston motion in packing stage was initially emulated by the Dynamic feed system. According to complex changes of temperature, pressure and extra shear field, cross WLF model were selected as the constitutive laws for HDPE in this study. The melt flow distribution, variation of the melt temperature and shear field in sample were investigated in OPIM simulation, meanwhile the results were also compared with those of conventional injection molding (CIM) simulation. The results show that, in the OPIM process, HDPE melts could repeatedly pass through the cavity at lower viscosity by the strong reciprocating motion of pistons, creating the temperature gradient at the thickness direction and forming a strong shear field, thus inducing the molecular chains to straighten and further form the shish-kebab structures. Finally, The real morphology and structure of OPIM and CIM samples were characterized by 2D-WAXD¡¢SEM. The results show a higher orientation and more shish-kebab structure in OPIM compared with those in CIM. Melt flow traces observed by microscopy confirmed the multiple melt flow under the action of pistons in cavity. The simulation results are in good agreement with our experiment results. Finally, this article provide the theoretical OPIM process window for high-performance sample processing and new simulation ideas for special injection moldings additional external force field.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19104
[Abstract](276) [FullText HTML](188) [PDF 1025KB](17)
Abstract:
It is challenging to improve the processing performance of silicon-containing arylacetylene resins while ensuring their excellent thermal properties. In this work, we presented a combination screening method for designing low-viscosity silicon-containing arylacetylene resins. We first defined the dichlorosilane as the gene for combination in terms of the chemical synthesis routes. The genes are combined with alkynyl benzene to generate a series of candidate resins. Then the viscosity, density, and thermal decomposition temperature of the candidate resins were calculated by molecular connection index method. Two optimal resins (ESA-e and ESA-2e) with higher index were screened through defining an index¨C¨Ca ratio of thermal decomposition temperature to viscosity. To validate the screened results, molecular dynamics simulation was used to evaluate the properties of the two optimal resins. In addition, a comparision between the optimal resins and a tranditional resin (PSA-H) were made. It was found that the viscosity of the optimal resins is lower than that of PSA-H and that of ESA-2e is the lowest. However, the glass transition temperature of the optimal resins decreased. To improve both the thermal properties and processing performance of the resins, the optimal resins were blended with PSA-H. The viscosity, thermal properties, and mechanical properties of the blends were examined by MD simulation. The results suggested that both the thermal properties and processing performance of the resins can be balanced via blending. The work provided a rapid method for the design and development of new resins. Moreover, the combination screening method can be generalized to the design of other advanced polymers.
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19103
[Abstract](280) [FullText HTML](237) [PDF 1255KB](37)
Abstract:
Good solubility is the premise in solution processing of conjugated polymers while strong ¦Ð-¦Ð interaction in the main chain is generally the main cause for bad dissolution. In this paper, our strategy is intruducing the auxiliary solvent and repeat unit with the similar structure as solvent in the main chain for good solubility of conjugated polymer. Based on the well dissolution between the auxiliary solvent and polymer repeat units induce a quasi-single polymer chain and advanced self-assembly, conjugated polymer coils and reversible supramolecular gels were acheived. R-limonene was added into chlorobenzene as the auxiliary solvent for the well solubility of poly(2-(4-(3',7'-dimethyloctylo-xyphenyl)-1,4-pheny-lene-vinylene (P-PPV). Atomic force microscope (AFM) images of the spin-coated films with solutions of low concentration showed the isolated P-PPV polymer coils and the fine structure inside the coils in chlorobenzene/R-limonene mixture; while with the absence of R-limonene, the packing of sub-polymer chain was clearly observed. In concentrated solution, P-PPV formed a reversible supramolecular gel at the concentration of 2 mg mL?1 with good temperature response characteristics in chlorobenzene/R-limonene mixture, and the gel temperature of P-PPV is in the range of 55 ¡ãC to ?35 ¡ãC. Aggregations with different curvatures were obtained in different solvents, which made us further understand the pliability of conjugated polymer. P-PPV molecular chains were dissolved by the enhanced solubility of alkyl sidechain and phenylene ethylene, that made it became pliable and then entangled, which allowed the assembly of polymer coils with high curvature and supramolecular gel with high ratio of solvent wrap. The fluorescence quantum yield and fluorescence lifetime were both improved in conjugated polymer coils and reversible supramolecular gels, but the physical cross-linking points by ¦Ð-¦Ð interaction showed low energy level as those of charge trap sites, where the mobility became lower. In the organic light emitting diodes (OLED), the uniform physical cross-linking network made the structure of P-PPV more stable and could effectively improve the stability, brightness, and lifetime of the device.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19081
[Abstract](282) [FullText HTML](181) [PDF 1240KB](9)
Abstract:
A series of novel amino-functionalized isotactic polypropylenes with high molecular weight and satisfying functional comonomer incorporation were prepared by direct copolymerization of propylene and ¦Á-olefins carrying carbazole functional groups. The homogeneous non-metallocene catalyst system consisting of dimethyl(pyridylamido)Hf(IV) complex, [Ph3C][B(C6F5)4], and AliBu3 showed good tolerance to carbazole groups and promoted the copolymerization of propylene with 11-carbazole-1-undecene effectively under mild reaction conditions, in which very high catalytic activity (up to 4.08 ¡Á 106 gpolymer molCat.?1 h?1) was achieved. The functional copolymers obtained possessed high molecular weight (up to 7.02 ¡Á 105) and tacticity ([mmmm] > 99%), as well as decent incorporation of carbazole functional groups (up to 13.5 mol%). Besides, DSC and TGA results verified the excellent thermostability of most copolymer products by giving decomposition temperatures around 450 ¡ãC as well as high melting points. Representative physical properties such as hydrophilicity, mechanical performance, and fluorescent characteristics of these iPPs functionalized by carbazole groups have also been explored. The increased incorporation of 11-carbazole-1-undecene monomer could reduce the water contact angle gradually and thus make significant improvement in surface properties; the copolymers became hydrophilic when comonomer incorporation exceeded 4.1 mol%. In terms of the mechanical properties, elongation at break of the copolymer barely increased at low incorporation (1.2 mol%), and the material still showed typical attributes of rigidity and brittleness. As more 11-carbazole-1-undecene monomer was incorporated (> 6.2 mol%), toughness of the materials was dramatically enhanced yet their stiffness was inevitably sacrificed. In addition, the introduction of carbazole group endowed the copolymers with unique fluorescent characteristics¡ªthey could emit purple fluorescence under 365 nm UV light in both solution and film states, thereby making this kind of functional polypropylene materials valuable and promising for the extensive applications in optoelectronic devices.
ËÄÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19053
[Abstract](385) [FullText HTML](263) [PDF 822KB](40)
Abstract:
To improve the hydrophilic properties of poly(propylene carbonate) (PPC), hydroxyl-functionalized PPC (PPC-OH) were prepared by two steps. First, PPC containing o-nitrobenzyl (ONB) protecting groups (PPC-ONB) were synthesized by terpolymerization reactions of 2-{[(2-nitrophenyl)methoxy]-methyl}oxirane (monomer a), propylene oxide (PO), and CO2 over SalenCo(III)Cl/bis(triphenylphosphine)iminium chloride (PPNCl) catalyst system. 1H-NMR result showed that the PPC-ONB was a random copolymer with monomer a randomly inserted. Then PPC-OH were obtained with the removal of o-nitrobenzyl (ONB) protecting groups under ultraviolet (UV) irradiation. PPC-ONB were synthesized with various feed ratios of the monomer a and different reaction time. Based on the analysis of 1H-NMR, 13C-NMR, gel permeation chromatography (GPC), and differential scanning calorimeter (DSC), SalenCo(III)Cl catalyst performed high reactivity and high selectivity (>94%). The polycarbonate exhibited excellent regioselectivity and perfect alternating copolymerization of CO2 and PO with the carbonate linkages up to 98%, and the head-to-tail linkage (HT) up to 99%. With the increase of the feed ratios of the monomer a, the polymer ratio of the monomer a increased to 19.4% without sacrificing the reactive activity, while the molecular weight (Mn) decreased slightly owing to the better reactivity of monomer a. The glass transition temperatures (Tg) were in the range of 35.7 ? 38.9 ¡ãC. The kinetics of deprotection by UV irradiation proved that the ONB protecting groups could be carried out efficiently within minutes. And the characterization of polymer by 1H-NMR, Fourier transform infrared spectrometer (FTIR) and GPC showed that the ONB protecting groups were removed and the ¨DOH was observed. Meanwhile, no degradation of polymer backbone occurred. The contact angle (CA) measurement of PPC-ONB and PPC-OH displayed a difference in hydrophilia. The hydrophilia of PPC-OH has been greatly improved compared with PPC-ONB due to the increase in polarity, and the CA of PPC-OH decreased from 78.3¡ã to 58.6¡ã when the molar ratio of ¨DOH increased to 19.4%.
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19080
[Abstract](286) [FullText HTML](215) [PDF 809KB](8)
Abstract:
Ring-opening polymerization of lactide (LA) is one of the most important techniques to synthesize poly(lactic acid) (PLA). In this work, a series of organocatalysts have been prepared for both solution polymerization and bulk polymerization of LA at ambient conditions. Derived from the facile reactions between phthalimide and quaternaryammonium salt, these catalysts are inexpensive and stable in air. Tetraethylammonium 2-aminobenzoate (TEACB) (catalyst a) was first applied to polymerize LLA in toluene solvent, and a conversion of 42.7% was achieved after the reaction proceeded at 25 ¡ãC for 1 h. Orthogonal experiments suggested that the optimum condition was reaction temperature of 75 ¡ãC, reaction time of 4 h, and the molar ratio of lactide:catalyst a:alkoxide equal to 200:10:1, which afforded PLA product with molecular weight of 8.03 kg¡¤mol¨C1, polydispersity index (PDI) of 1.53, and a high conversion of 88.5%. Next, bulk polymerization of LLA was carried out at different temperatures to explore the effects of initiator, alcohol salt, reaction time, and the molar ratio of lactide:catalyst:alkoxide. The catalytic activity of the catalysts depended largely on their chemical structures. Under the same reaction temperature, catalyst b with larger cation part led to a higher conversion; meanwhile, catalysts a and b with phenyl group in the anionic part were more active than catalyst c bearing an aliphatic group although the latter produced PLA with higher molecular weight and narrower molecular weight distribution. The catalysts developed in this study worked well in the absence of alkoxide, whilst alkoxide and alcohol could improve the performance of the catalyst system. LLA polymerizations could be conveniently performed under atmospheric conditions and increasing temperature resulted in PLA products with higher molecular weight and narrower molecular weight distribution. The conversion reached up to 95.7% after polymerization at 150 ¡ãC, in which the Mn and PDI of the PLA product equaled 2.57 kg¡¤mol¨C1 and 1.24, respectively. DSC measurements indicated that PLAs obtained via varied methods displayed similar melting temperatures in the range of 130 ¨C 134 ¡ãC. Further, cooperative dual activation of both the monomer and the initiator/chain-end could be confirmed based on MALDI-TOF-MS analyses. This novel catalyst system possesses specific monocomponent hetero-bifunction with H-bonding capability.
ÈýÐ£ ,?doi: 10.11777/j.issn1000-3304.2019.19076
[Abstract](359) [FullText HTML](268) [PDF 1043KB](15)
Abstract:
We developped a material genome approach to accelerate the design and synthesis of novel heat-resistant silicon-containing arylacetylene resins. The material genome approach is based on the consideration that silicon-containing arylacetylene resins can be regard as a combination of silane and diyne units which can be defined as genes used for combination screening. The approach presented here contains two steps. In the first step, various kinds of diynes were collected from the chemical database as candidate structures; the bond dissociation energy (BDE) reflecting heat resistance of resins was calculated; the candidate structures were preliminarily screened with the criteria of BDE; and finally 16 diynes with high BDE were obtained. In the second step, LUMO-HOMO and 50% decomposition temperature (Td50) were calculated by density functional theory and molecular connection index method, respectively; and the optimized gene was obtained out of 16 candidate structures. The screened resin is poly(diphenylsilylene-ethynylene-naphthalene-ethynylene) (abbreviated as PSNP) containing the gene of 2,7-diethynylnaphthalene. To verify the screened results, we first synthsized the PSNP by Sonogashira coupling of dichlorodiphenylsilane and 2,7-diethynylnaphthalene. The molecular structure of PSNP resin was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR). The curing process of PSNP resin was studied by differential scanning calorimetry (DSC). The results show that the curing peak temperature (Tpeak) of PSNP and the enthalpy of exothermic reaction are 212 ¡ãC and 173.8 J/g, respectively, which are lower than those of traditional poly(silylene-acetylenearyleneacetylene) resin (PSA). The cured PSNP resin exhibits excellent heat-resistance, where the 5% decomposition temperature (Td5) of the cured PSNP resin is 561 ¡ãC. The properties of the resin are consistent with the theoretical design results, which confirms the validity of material genome method for structural screening of new silicon-containing arylacetylene resins.
×îÐÂÂ¼ÓÃ ,?doi: 10.11777/j.issn1000-3304.2019.19135
[Abstract](55) [PDF 0KB](1)
Abstract:
In the present work, based on the coordination capability of nitrile groups in nitrile rubber (NBR) with metal ions, a novel type of rubber material with sacrificial domains was designed. Specifically, copper sulfate (CuSO4) and vulcanization package were introduced into styrene-butadiene rubber (SBR)/NBR blend by mechanical mixing and hot pressing. As a result, SBR with sulfur crosslinkings are formed as continous phases while the NBR mainly crosslinked by Cu (II)-nitrile coordination bonds are acted as dispersed phases, which are used as deformable domains to reinforce SBR. With the increasing concentration of coordination bonds in dispersed phase, both strength and modulus of the rubber improve rapidly. When 20 wt% NBR was introduced, the strength and modulus of SBR are increased by 2.6-fold and 3.2-fold, respectively. The significant reinforcing effect of this system is attributed to the strong yet deformable domains. The strong domains have hydrodynamic effect, which greatly improve the moduli of the samples. On the other hand, upon external stress, the loading can be rapidly transferred from SBR matrix to the domains owning to strong interfacial interactions, forcing the domains to develop high-elastic deformation prior to the rupture of SBR chains and dissipate mechanical energy, thus significantly enhancing the toughness of the rubber. This forced high-elastic deformation in domains can be recoverd through relaxation at a high temperature to fully restore the mechanical properties. Overall, this work provides a new way for the reinforcement of non-polar rubber through the design of deformable domains.
×îÐÂÂ¼ÓÃ ,?doi: 10.11777/j.issn1000-3304.2019.19106
[Abstract](121) [PDF 0KB](0)
Abstract:
Multi-responsive polymers, with cluster-induced luminescence (CIE) featured by non-conjugated chromophores, have attracted great attention in recent years, and the relevant studies have been focused mainly on the polymers with aliphatic amines and carbonyl groups. Although the CIE behaviors have been previously reported for ethylene glycol based polymers, studies to correlate their luminescent properties to their stimuli-responsiveness are rarely avaible. In this paper, P(OEGA-MAA), a copolymer responsive to temperature, pH and salt, was prepared by free radical copolymerization of oligo(ethylene glycol) methyl ether acrylate (OEGA) with methylacrylic acid (MAA) in ethanol. The structure of P(OEGA-MAA) was characterized by 1H NMR and its molecular weight determined by GPC. The evolution of light transmittance of the water solution of P(OEGA-MAA) with temperature was measured under different conditions and its fluorescence performance was characterized. The results show that P(OEGA-MAA) is not only responsive to temperature, pH and salt, but also emits visible blue fluorescence under UV. Effects of the polymer composition, pH and salt concentration on the lower critical solution temperature (LCST) and fluorescence properties are studied. And the relationship between fluorescence properties and phase transition process is also descibed. With OEGA content decreased in the polymer, the LCST in its aqueous solution (2.0 mg/mL, pH=1) decreased, and the corresponding fluorescence intensity increased first with OEGA content of up to 33 mol% (OEGA/MAA=3.3/6.7, sample P7), where it reached a maximum, and followed by a decrease with further decrease in OEGA. Effects of pH and NaCl concentration were also studied with P7 as an example. With increased pH in the aqueous solution (2.0 mg/mL) of P7, the LCST increased and the fluorescence intensity decreased; With the increase in NaCl concentration, the LCST decreased, while no obverious change was detected for the fluorescence intensity. Furthermore, when the polymer concentration was increased, the LCST decreased, and the fluorescence intensity increased obviously. All the results indicate that the fluorescence emission was caused by aggregation of oxygen atoms in polymer segments. This study provides therefore a novel type of materials for potential applications in biomedical fields, and it is also of great significance for understanding the luminescence mechanism of PEG-based stimuli-responsive polymers.
×îÐÂÂ¼ÓÃ ,?doi: 10.11777/j.issn1000-3304.2019.19136
[Abstract](111) [PDF 0KB](1)
Abstract:
Polymer synthetic chemistry is a scientific discipline which mainly studies molecular design, synthesis and modification of high molecular weight compounds. It provides indispensable materials that guarantee social progress, improvement of human living standards, and national security. Since the founding of the People's Republic of China 70 years ago, Chinese scholars have made significant contributions to the development of this field. Important achievements include but not limited to design and synthesis of new monomers and polymers, development of highly efficient and environmentally benign catalysts and new polymerization reactions, optimization of key synthetic pathways, and establishment of relationships of new structures and properties. This paper summarizes the research and development of synthetic polymer chemistry in China, and anticipitates a bright future in the development of various polymerization reactions, control of polymer topology as well as design, synthesis and polymerization of monomers from biomass sources.
×îÐÂÂ¼ÓÃ ,?doi: 10.11777/j.issn1000-3304.2019.19133
[Abstract](52) [PDF 2418KB](2)
Abstract:
The polymeric drug delivery systems (DDS) have showed promising potential for improving cancer therapy, which can lengthen the blood circulation and minimize the adverse effect of chemotherapeutics. Despite promising, the therapeutic performance of polymeric-based DDS is hurdled by a series of physiological barriers, including limited tumor accumulation, restricted tumor penetration, insufficient cellular uptake, and slow drug release inside the tumor cells. It has been well-investigated that there is an acidic microenvironment inside the solid tumors due to the abnormal glucose metabolism of tumor cells. Moreover, the subcellular organelles including endosome and lysosome display much lower acidic pH than that of cytosol. The extracellular and intracellular acidic microenvironment have thus been exploited as both a trigger and target for tumor-targeted drug delivery. In this review article, we summarized our recent advances to develop acid-responsive polymeric DDS by taking the advantage of the acidic microenvironment of tumor tissue and tumor cells. We particularly highlighted the acid-responsive chemical bonds and components employed for constructing the acid-activatable DDS. These acid-activatable nanovectors have been exploited for combating the physiological barriers by surface charge conversion, nanostructure dissociation, and ligand presentation. We also provided a perspective regarding of the challenges and opportunities about clinical translation of the stimuli-activatable DDS.

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2019, 50(8).
[Abstract](95) [PDF 2914KB](16)
Abstract:
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2019, 50(8): 761-763. doi: 10.11777/j.issn1000-3304.2019.19123
[Abstract](372) [FullText HTML](272) [PDF 502KB](41)
Abstract:
To synthesize cyclic polymers with definite topological structure is always a challenging topic in polymer chemistry. Recently, Xie and coworkers at East China Normal University developed a blocking cyclization route to synthesize cyclic polymers with controllable topology, and synthesized a series of A(B2A)n (n = 1, 2, and 3) type cyclic copolymers with well-defined ring size (the repeat unit was 40 ? 400) and ring number (1 ? 3), mainly by successive ring-opening metathesis polymerization (ROMP) of alternating addition of di- and monofunctional norbornene monomers in a one-pot process. This blocking cyclization strategy, unlike the traditional ring-closure and ring-expansion techniques, can precede at high monomer concentration (0.02 mol L?1) producing very high cyclization efficiency, which has broken through the limitation of the previous two traditional cyclizing routes, and thus can be considered as the third route as a versatile platform to cyclic polymers by commercial Grubbs catalyst and conventional ROMP.
2019, 50(8): 764-774. doi: 10.11777/j.issn1000-3304.2019.19069
[Abstract](599) [FullText HTML](350) [PDF 2636KB](130)
Abstract:
Benefiting from intensive size effect and surface effect arising from thin fibers, micro/nano-fibrous membranes exhibit many fascinating properties and have become a hot spot and leading edge in the fiber materials. Among the existing processing approaches for micro/nano-fibers, electrospinning has proven to be one of the most effective and promising method due to its integrated characteristics, including broad availability to varieties of polymers, adjustable porous structure, and superior technological convergence. In recent years, our research group have endeavored systematic researches on the controllable fabrication and applications of electrospun micro/nano-fibrous materials, especially in the terms of ultra-thin nanonets, compactly bonded membranes and porous fibrous aerogels. This review mainly puts focus on the formation mechanisms and applications of these distinctive micro/nano-fibrous materials, which are summarized as follows. Firstly, the two-dimensional nanonets with extremely small diameters (< 20 nm) are fabricated by a novel electrospinning/netting technique, and the deformation-phase transition of the charged jets/droplets from polymer solution during the period is also revealed, which have broken the bottleneck of the thinning on diameter of electrospun fibers. And the novel nanonets demonstrate lower air resistance due to the slip flow of air molecules on the periphery of nanofibers, holding great promise as an exceptional candidate for air filtration. Secondly, compactly bonded membranes with stable porous structures are constructed directly through the regulation of the relative humidity, and the effects of relative humidity on electrospinning jet stretching and solidification are investigated. Additionally, hydrophobicly modified compactly bonded membranes demonstrate excellent waterproofness and breathability, thus implying their potential application in selective separation of gas-liquid medium. Thirdly, the ultralight polymeric micro/nano-fibrous aerogels with hierarchical cellular structure and superelasticity are prepared via a novel three-dimensional fibrous framework reconstruction method, which exhibit the integrated properties of extremely low density (minimum of 0.12 mg/cm3), super recyclable compressibility and multifunctionality of combining the thermal insulation, sound absorption, emulsion separation and elasticity-responsive electric conduction. The future perspectives of micro/nano-fibrous materials were also given at the end of this review.
2019, 50(8): 775-807. doi: 10.11777/j.issn1000-3304.2019.19062
[Abstract](415) [FullText HTML](240) [PDF 4929KB](19)
Abstract:
Conjugated polymers have attracted much attention due to their unique electronic properties and solution processing methods. The rigid and planar conformational backbone manifests extended ¦Ð-system and the flexible alkyl chain assures the sufficient solubility, which contribute to their tuneable physical and chemical properties and increase the tolerance of film forming and mechanical flexibility. In general, the orthogonal design of functional fragments for conjugated polymers make it accessible for ¦Ð-stacking of conjugated segments and lamellar stacking of interchain interactions. Short-range aggregates or long-range microcrystals would be selectively and/or successively formed by controlling their chemical structures and processing conditions. Such stacking structure in the phase-separated domain is crucial to the high efficient performance of bulk heterojunction solar cells. The aggregation structure of some typical conjugated polymers has recently been reviewed with a view to providing reference for the development of optoelectrics in this study. Here, D-A copolymers based on oligothiophene, dithiophene, benzothiophene and thiophene derivatives, two-dimensional conjugated polymers and block copolymers are introduced in detail. The aggregation structure of a series of conjugated polymers is systematically summarized by using the different processing techniques, such as selective counterpart components, treating solvents and annealing temperature. In addition, the intrinsic motivation of the controllable aggregation structure is discussed from the aspects of molecular weight and side chain groups.
2019, 50(8): 808-815. doi: 10.11777/j.issn1000-3304.2019.19026
[Abstract](810) [FullText HTML](318) [PDF 928KB](29)
Abstract:
Polymeric vesicles have important applications in biomedicine, nuclear magnetic imaging, nanoreactors, and catalyst fields. Amphiphiic block copolymer nanoparticles with different morphologies (such as vesicles and spheres), sizes and surface chemical properties have been successfully prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA). Generally, it is difficult for researchers to obtain pure vesicles with different sizes. In this study, we report an efficient approach to produce block copolymers vesicles by PISA. A one-pot, facile method for the synthesis of nano-objects composed of amphiphilic poly(4-vinylpyridine)-b-poly(4-vinylpyridine-r-styrene) block copolymer, P4VP-b-P(4VP-r-St), is introduced by P4VP trithiocarbonate macro-RAFT agent mediated dispersion copolymerization of 4VP and St in ethanol/water mixture. It is found that the morphology of P4VP-b-P(4VP-r-St) diblock copolymer nano-objects like spherical micelles, worms, and vesicles can be easily tuned either by changing the degree of polymerization of the random P(4VP-r-St) block, the amount of 4VP comonomer, solvent composition and the ratio of the degree of polymerization of PSt and P4VP segments. Among them, by adding a small amount of 4VP comonomer during the dispersion RAFT polymerization of St, the final morphology of the block copolymer can be greatly affected, pure vesicle can be formed and the size can be adjusted more effectively. Compared with the dispersion RAFT polymerization of St, the advantage of the dispersion RAFT copolymerization by utilizing residual solvophilic monomer to tune the block copolymer morphology is demonstrated. It is believed to be a novel, convenient and efficient protocol for the control of the morphology and size of the block copolymer nano-objects fabricated by PISA. The polymerization shows characteristic features of " living¡±/controlled radical polymerization and the experimental results are confirmed by gel permeation chromatography (GPC), dynamic light scattering (DLS), transmission electron microscopy (TEM) and 1H-NMR. Due to diverse potential applications of polymer vesicles, the results of this study are of great importance for the theoretical design and application of PISA strategies.
2019, 50(8): 816-825. doi: 10.11777/j.issn1000-3304.2019.19041
[Abstract](391) [FullText HTML](218) [PDF 1049KB](24)
Abstract:
Medium molecular weight multi-block copolymers of poly(L-lactic acid) (PLLA) and poly(butylene succinate) (PBS), MMW-mb(PLLA-PBS)s, were controlled-synthesized via melt block copolycondensation (bc-MP) of two macromonomers, i.e. oligo-PLLA (OPLLA) and oligo-PBS (OPBS) with four creatinine (CR)-based organic guanidine (OG) catalysts. The catalytic performance of the four OGs is far superior to that of Sn(Oct)2 in terms of molecular weight (Mw = 14.2 ¨C 28.6 kDa versus 12.9 kDa), apparent yield of synthesized block copolymers (74.15% ¨C 82.02%), as well as the by-product (lactide, LA) yield (1.08% ¨C 6.71% versus 20.7%). Among the OGs, creatinine acetate (CRA) shows the best catalytic performance. 1H-NMR structural characterization of the MMW-mb(PLLA-PBS) synthesized with CRA indicates that the measured molar ratio of the two blocks, fOPLLA/fOPBS, of MMW-mb(PLLA-PBS) is 89.3/10.7, close to the designed value (\begin{document}$\,f\!_{\rm{OPLLA}_0}$\end{document}/\begin{document}$\,f\!_{\rm OPBS_0}$\end{document} = 90/10). A high molecular weight (Mw = 114.0 kDa) block copolymer, HMW-mb(PLLA-PBS), was synthesized via bc-MP of two macromonomers with CRA for the first time. The tensile strength of the block copolymer (50.67 MPa) is close to that of PLLA (54.10 MPa), and the elongation at break of the copolymer (BE = 60.66%) is 15 times greater than that of PLLA. TGA analysis indicates that the original decomposition temperature (Td,0 = 272 ¡ãC) is 22 ¡ãC higher than that of PLLA. The molar ratio of two blocks, fOPLLA/fOPBS (89.7/10.3) in HMW-mb(PLLA-PBS), measured by 1H-NMR, is very close to the designed value (90/10). This is the first controlled synthesis of multi-block copolymer of PLLA-PBS via bc-MP with a biogenic guanidine-based catalyst CRA. The mechanism of the bc-MP is proposed on the basis of experimental investigation.
2019, 50(8): 826-833. doi: 10.11777/j.issn1000-3304.2019.19020
[Abstract](653) [FullText HTML](168) [PDF 1141KB](19)
Abstract:
2019, 50(8): 834-840. doi: 10.11777/j.issn1000-3304.2019.19023
[Abstract](633) [FullText HTML](230) [PDF 783KB](26)
Abstract:
The concentration dependence of chain conformation and disorder-order transition of poly(3-hexylthiophene-2,5-diyl) (P3HT) in toluene solution at room temperature are investigated by multiple characterizations including photoluminescence spectroscopy (PL), UV-Vis absorption spectroscopy (UV-Vis), synchrotron radiation X-ray scattering technique (SAXS), and atomic force microscopy (AFM). The results indicate a critical concentration of ~ 5 mg/mL, at which the interchain interaction and chain aggregation state vary pronouncedly. In the dilute solution (< 5 mg/mL), P3HT chains maintain as independent random coils with negligible interchain interactions despite of regional segmental aggregate formation within the coils as revealed by PL and SAXS measurements. With the solution concentration exceeding the critical value of 5 mg/mL, the chain collapse takes place and the radius of gyration of the molecular chains decreases due to the strengthened ¦Ð-¦Ð couplings among coils. The higher concentration of the solution leads to higher interchain entanglement and more local formation of rod-like segmental aggregates. The amount of the local segment aggregation is found to positively correlated with the concentration, while the radius of gyration and chain conformation exhibit nearly no variation any more at the concentrated solutions. SAXS data display a decreased power law of the concentrated solutions with respect to the dilute solutions, suggesting a lower dimension of the form factor and an improved interchain aggregation in the concentrated solution. This is in good agreement with the UV absorption and PL results. This concentration dependence of the regional chain disorder-order transition in P3HT/toluene solution is further verified to exert great influence on the final crystalline morphologies of the spin-casted films. The segmental aggregated orderings in solution can be effectively transferred to the thin films through namely the " memory effect¡± during the solution processing, resulting in nanowire structures and higher crystallinity of the films for the higher concentration solution.
2019, 50(8): 841-849. doi: 10.11777/j.issn1000-3304.2019.19024
[Abstract](338) [FullText HTML](226) [PDF 1332KB](20)
Abstract:
The glass transition, crystallization, and melting behaviors of oligomer poly(L-lactide) (PLLA) confined in anodic aluminum oxide (AAO) nanopores were invesitgated by calorimetry. Compared with the bulk counterpart, PLLA located inside AAO nanopores showed frustrated crystallization during the cooling process, and the crystallization enthalpy gradually decreased with the reduction of pore size. In large nanopores, the crystallization peaks of PLLA nanorods were very close to that of bulk sample, which indicated the predomination of heterogeneous nucleation. Meanwhile, the nonisothermal crystallization results displayed that temperature dependence of nucleation rate of PLLA in nanopores was weaker than that in bulk state. As the diameter of nanopore was smaller than 28 nm, the crystallization peak disappeared. The glass state of PLLA nanorods exhibited double glass transition temperatures (Tgs), the higher Tg attributed to chains in the interfacial adsorbed layer adjacent to pore walls, and the lower Tg belonged to chains in the pore center. The two Tgs showed opposite pore size dependences¡ªthe lower one decreased with the reduction of pore size, while the higher one increased. During the heating process, PLLA confined in nanopores showed the pronounced cold crystallization phenomenon, which took place at higher temperatures and the peak was much broader than that of bulk state, which could be ascribed to the supressed nucleation rate, the poor nucleation activity, and the broad nucleation dispersion in PLLA nanorods. Apart form the influence of nucleation, hetergeneous chain mobilities in nanopores also played an important role. Due to the existence of adsorbed layer, surface induced nucleation was hindered. Interestingly, by the nonisothermal crystallization experiments, PLLA chains in the interfacial layer and pore center displayed independent cold crystallization behaviors, and the latter happened at the higher temperatures. Finally, the interfacial effect gradually dominated as the pore size decreased. PLLA crystals formed in small nanopores became unstable, obvious melting-recrystallization phenomena occurred, and the crystallinity and melting temperature of PLLA crystals were lower in smaller nanopores.
2019, 50(8): 850-856. doi: 10.11777/j.issn1000-3304.2019.19030
[Abstract](818) [FullText HTML](578) [PDF 1096KB](36)
Abstract:
A series of microcellular polypropylene (PP) electrical boxes were fabricated by microcellular injection molding with supercritical nitrogen (Sc-N2) as the physical foaming agent. The effects of higher injection speeds (250 and 290 mm/s) on the cellular structure, unfoamed skin layer thickness, and warpage of the microcellular boxes were quantitatively investigated. According to the simulated gapwise distributions of shear rate, temperature, viscosity, and pressure of PP melt/Sc-N2 solution at the last moment of the filling stage in the molding of the PP boxes, the formation mechanisms of cellular structure and skin layer within the walls of the boxes were analyzed in detail. It was demonstrated that microcellular cells with smaller diameters (less than 90 ¦Ìm) were developed at the core layer of the boxes. This is mainly because higher injection speeds led to higher pressure drop rate and shear rate, which thereby promoted bubble nucleation. It should be noted that tiny cell area with diameters less than 20 ¦Ìm and more regular shape appeared near the skin layer of the boxes. This is due to the synthetic effects of higher shear stress combined with lower melt temperature. Along the filling direction, an exponential relationship was found between density and mean diameter of the cells within box sidewall, and the skin layer thickness increased in a nearly linear manner. The latter is mainly attributed to an almost linear decrease in the corresponding surface temperature. Warpages at the open end of the boxes were decreased through increasing the injection speed from 250 mm/s to 290 mm/s. The results demonstrate that more uniform and compact cellular structure as well as thinner unfoamed skin layer is beneficial to lowering the warpage of microcellular injection molded parts. This is worthy of further investigation in the future work.
2019, 50(8): 857-862. doi: 10.11777/j.issn1000-3304.2019.19032
[Abstract](191) [FullText HTML](126) [PDF 1028KB](27)
Abstract:
Poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) can form hydrogen-bonded polymer complex. A PAA/PEO homogenous solution can be obtained by adding NaOH into the mixture to restrict the hydrogen bonding between PAA and PEO. First, PAA was dissolved in 20 mL of NaOH aqueous solution and PEO was dissolved in 20 mL of distilled water with the total mass of PAA and PEO of 3.48 g. After stirred for 6 h and centrifuged in the deaeration system at 3500 r/min for 10 min, the mixture was blade coated onto a PTFE plate through an adjustable film applicator with the thickness of 2 mm, and dried in the ambient environment to obtain PAA/PEO films. The effects of film composition and acid treatment on the structures and mechanical properties of the films were studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), wide angle X-ray diffraction (XRD), and mechanical streching machine. The crystallization behavior of PEO and the mechanical properties of the films showed strong dependence on the hydrogen bonding between PAA and PEO. The elongation increased while the tensile strenghth and the Young¡¯s modulus decreased first and then increased with the increasing PEO content in the films. After incubation in a pH = 1 solution for 3 min, the hydrogen bonding between PAA and PEO was enhanced. Compared with the film without acid treatment, the flexibility of the film was greatly enhanced after acid incubation. In particular, Young¡¯s modulus of the film (n(AA):n(EO) = 1:3) before acid treatment was 426 MPa while it declined to 3 MPa after acid incubation. Namely, when the hydrogen bonding between PAA and PEO became weak, PEO would crystallize and the film performed like a plastic material. When the hydrogen bonding between PAA and PEO became strong, the crystallization of PEO was restricted and the film acted as a rubber material.
• Editor:?Xi Zhang

Establishment Time:?1957

?Chinese Chemical Society