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2019 Volume 50 Issue 12
2019, 50(12):
Abstract:
下载PDF文件可查看高分子学报 2019 年 第 50 卷 第 1 ~ 12 期总目次
下载PDF文件可查看高分子学报 2019 年 第 50 卷 第 1 ~ 12 期总目次
2019, 50(12):
Abstract:
下载PDF文件可查看本期的封面、目录和图文摘要。
下载PDF文件可查看本期的封面、目录和图文摘要。
2019, 50(12): 1239-1252
doi: 10.11777/j.issn1000-3304.2019.19153
Abstract:
Different from other members in the carbon material family, graphyne, first synthesized in 2010, has sp hybridized carbons and a natural band gap. According to many studies on optoelectronic devices, the recombination of electrons and holes is an important issue, and the excellent photoelectric properties of graphyne such as high carrier mobility and π-conjugated structure can make it an important candidate material in the fields of photocatalysis, electrocatalysis, batteries, etc. However, there are still problems remaining for the direct application of unmodified graphyne owing to its inert surface and fixed band gap. The high activity of acetylenic bond units in the graphyne provides a good platform for chemical modification and doping. Therefore, the energy band structure and semiconductor performance of graphyne can be regulated by simple solution mixing, hydrothermal reaction, and redox method to achieve material hybridization or hetero atom doping, so that the graphyne will fulfill the requirements of photoelectric devices for a semiconductor material. Many studies have been concentrated on this topic, and numerous achievements have been made over the years. In this review article, the properties and synthesis methods of graphdiyne are firstly introduced, followed by a systematic summary about the mechanism of different atomic doping changes which could help in design of precursor molecules and subsequent synthesis of graphyne derivatives. The promotion effect of graphyne hybridization on charge transfer and its specific mechanism are then detailedly illustrated. The latest research progresses of graphyne and graphyne derivatives in practical applications including photoelectrocatalysis, dye sensitized solar cell, and perovskite solar cell are further discussed, while some problems existing in the current research of this field are also listed. Our review concludes with the proposal that research focuses in the future should be shifted from theoretical calculation to specific experiment and the mechanism in the process requires better understanding, so as to push forward the studies on graphyne and further improve material properties.
Different from other members in the carbon material family, graphyne, first synthesized in 2010, has sp hybridized carbons and a natural band gap. According to many studies on optoelectronic devices, the recombination of electrons and holes is an important issue, and the excellent photoelectric properties of graphyne such as high carrier mobility and π-conjugated structure can make it an important candidate material in the fields of photocatalysis, electrocatalysis, batteries, etc. However, there are still problems remaining for the direct application of unmodified graphyne owing to its inert surface and fixed band gap. The high activity of acetylenic bond units in the graphyne provides a good platform for chemical modification and doping. Therefore, the energy band structure and semiconductor performance of graphyne can be regulated by simple solution mixing, hydrothermal reaction, and redox method to achieve material hybridization or hetero atom doping, so that the graphyne will fulfill the requirements of photoelectric devices for a semiconductor material. Many studies have been concentrated on this topic, and numerous achievements have been made over the years. In this review article, the properties and synthesis methods of graphdiyne are firstly introduced, followed by a systematic summary about the mechanism of different atomic doping changes which could help in design of precursor molecules and subsequent synthesis of graphyne derivatives. The promotion effect of graphyne hybridization on charge transfer and its specific mechanism are then detailedly illustrated. The latest research progresses of graphyne and graphyne derivatives in practical applications including photoelectrocatalysis, dye sensitized solar cell, and perovskite solar cell are further discussed, while some problems existing in the current research of this field are also listed. Our review concludes with the proposal that research focuses in the future should be shifted from theoretical calculation to specific experiment and the mechanism in the process requires better understanding, so as to push forward the studies on graphyne and further improve material properties.
2019, 50(12): 1253-1262
doi: 10.11777/j.issn1000-3304.2019.19157
Abstract:
Featured by its outstanding thermo-oxidative stability and excellent mechanical properties, polyimide has aroused growing research interests. The hierarchical structure of polyimide (PI), which largely influences its thermal, mechanical, and photoelectric properties, can be well adjusted by carefully regulating the chemical composition. In this review, we primarily focus on the employment of molecular simulation for unravelling and interpreting the structure-property relationship of PI materials, and summarize the recent progress both at home and aboard on the research of multi-scale PI structures. The molecular chain structures of PI can be finely analyzed in terms of the chains conformation, characteristic ratio and torsion energy barrier, while the thermal and mechanical properties are properly explained from the perspective of molecular chain constitutions, chains movement and the packing state of PI chains. Meanwhile, the highly concerned force field has been used in molecular dynamic (MD) simulation of PI thermal-mechanical behaviours. MD simulation or Monte Carlo (MC) simulation also works well for understanding the gas separation performance of PI materials through the fractional free volume (FFV) of PI molecules or the dissolution and diffusion patterns of small molecules in novel PI framework with particular main-chain or side-chain structures. Furthermore, the studies on PI-based composites are basically concentrated on the exploration of interfacial properties between PI and other materials, including the simulated binding energy and small-scale interactions like the van der Waals forces and electrostatic interactions. The development trend of computer simulation in PI-related research is briefly discussed in the end, so as to provide valuable guidance for the performance optimization of PI materials as well as some useful thoughts on the design and preparation of functional PI molecules.
Featured by its outstanding thermo-oxidative stability and excellent mechanical properties, polyimide has aroused growing research interests. The hierarchical structure of polyimide (PI), which largely influences its thermal, mechanical, and photoelectric properties, can be well adjusted by carefully regulating the chemical composition. In this review, we primarily focus on the employment of molecular simulation for unravelling and interpreting the structure-property relationship of PI materials, and summarize the recent progress both at home and aboard on the research of multi-scale PI structures. The molecular chain structures of PI can be finely analyzed in terms of the chains conformation, characteristic ratio and torsion energy barrier, while the thermal and mechanical properties are properly explained from the perspective of molecular chain constitutions, chains movement and the packing state of PI chains. Meanwhile, the highly concerned force field has been used in molecular dynamic (MD) simulation of PI thermal-mechanical behaviours. MD simulation or Monte Carlo (MC) simulation also works well for understanding the gas separation performance of PI materials through the fractional free volume (FFV) of PI molecules or the dissolution and diffusion patterns of small molecules in novel PI framework with particular main-chain or side-chain structures. Furthermore, the studies on PI-based composites are basically concentrated on the exploration of interfacial properties between PI and other materials, including the simulated binding energy and small-scale interactions like the van der Waals forces and electrostatic interactions. The development trend of computer simulation in PI-related research is briefly discussed in the end, so as to provide valuable guidance for the performance optimization of PI materials as well as some useful thoughts on the design and preparation of functional PI molecules.
2019, 50(12): 1263-1271
doi: 10.11777/j.issn1000-3304.2019.19093
Abstract:
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.
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.
2019, 50(12): 1272-1279
doi: 10.11777/j.issn1000-3304.2019.19092
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 °C. Such excellent energy storage and light responsiveness endowed this PBN film with potential applications in the field of space thermal management.
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 °C. Such excellent energy storage and light responsiveness endowed this PBN film with potential applications in the field of space thermal management.
2019, 50(12): 1280-1289
doi: 10.11777/j.issn1000-3304.2019.19103
Abstract:
Good solubility is the premise in solution processing of conjugated polymers while strong π-π 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 microscopy (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 °C to −35 °C. 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 π-π 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.
Good solubility is the premise in solution processing of conjugated polymers while strong π-π 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 microscopy (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 °C to −35 °C. 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 π-π 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.
2019, 50(12): 1290-1297
doi: 10.11777/j.issn1000-3304.2019.19080
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 °C for 1 h. Orthogonal experiments suggested that the optimum condition was reaction temperature of 75 °C, 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–1, 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 °C, in which the Mn and PDI of the PLA product equaled 2.57 kg·mol–1 and 1.24, respectively. DSC measurements indicated that PLAs obtained via varied methods displayed similar melting temperatures in the range of 130 – 134 °C. 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.
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 °C for 1 h. Orthogonal experiments suggested that the optimum condition was reaction temperature of 75 °C, 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–1, 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 °C, in which the Mn and PDI of the PLA product equaled 2.57 kg·mol–1 and 1.24, respectively. DSC measurements indicated that PLAs obtained via varied methods displayed similar melting temperatures in the range of 130 – 134 °C. 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.
2019, 50(12): 1298-1304
doi: 10.11777/j.issn1000-3304.2019.19086
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.
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.
2019, 50(12): 1305-1313
doi: 10.11777/j.issn1000-3304.2019.19099
Abstract:
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 °C, 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 °C. All of these PAI films exhibited ultralow thermal expansion with negative coefficient of thermal expansion (CTE) values from –6.87 ppm/°C to –3.84 ppm/°C even in a wide temperature range of 30 – 400 °C. 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 (Δn), 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 Δn values ranged from 0.2438 to 0.2621 as annealing temperature increased from 350 °C to 425 °C. 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.
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 °C, 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 °C. All of these PAI films exhibited ultralow thermal expansion with negative coefficient of thermal expansion (CTE) values from –6.87 ppm/°C to –3.84 ppm/°C even in a wide temperature range of 30 – 400 °C. 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 (Δn), 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 Δn values ranged from 0.2438 to 0.2621 as annealing temperature increased from 350 °C to 425 °C. 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.
2019, 50(12): 1314-1321
doi: 10.11777/j.issn1000-3304.2019.19106
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 of ethylene glycol-based polymers have been previously reported, studies that correlate their luminescent properties with their stimuli-responsiveness are rarely available. 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 was 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) not only has 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 describled. As 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 up to 33 mol% (OEGA/MAA = 3.3/6.7, sample P7 ), where it reached a maximum, 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.
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 of ethylene glycol-based polymers have been previously reported, studies that correlate their luminescent properties with their stimuli-responsiveness are rarely available. 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 was 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) not only has 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 describled. As 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 up to 33 mol% (OEGA/MAA = 3.3/6.7, sample P7 ), where it reached a maximum, 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.
2019, 50(12): 1322-1330
doi: 10.11777/j.issn1000-3304.2019.19104
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––a 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.
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––a 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.
2019, 50(12): 1331-1337
doi: 10.11777/j.issn1000-3304.2019.19107
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 that 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 increase of the particle activity, the translocation probability of polymer chain toward active bath increases quickly, and 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, resulting 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, it is found 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. The results may provide an insight into the translocation behavior of polymer chain, and help understand the non-equilibrium processes in living organisms.
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 that 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 increase of the particle activity, the translocation probability of polymer chain toward active bath increases quickly, and 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, resulting 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, it is found 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. The results may provide an insight into the translocation behavior of polymer chain, and help understand the non-equilibrium processes in living organisms.
2019, 50(12): 1338-1347
doi: 10.11777/j.issn1000-3304.2019.19108
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 °C, 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.
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 °C, 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.
2019, 50(12): 1348-1356
doi: 10.11777/j.issn1000-3304.2019.19111
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.
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.
2019, 50(12): 1357-1366
doi: 10.11777/j.issn1000-3304.2019.19132
Abstract:
Based on the analysis of uniaxial stress-strain curves, the quantitative relationship between the composition, structure and properties of elastomers can be obtained. So far, more than 30 constitutive models have been developed. 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 non-linear fitting of these modeling stress-strain curves using the coefficient of determination and Fréchet distance, the similarity and mathematical 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 undirectionally 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.
Based on the analysis of uniaxial stress-strain curves, the quantitative relationship between the composition, structure and properties of elastomers can be obtained. So far, more than 30 constitutive models have been developed. 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 non-linear fitting of these modeling stress-strain curves using the coefficient of determination and Fréchet distance, the similarity and mathematical 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 undirectionally 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.
