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2020 Volume 51 Issue 3
2020, 50(3):
Abstract:
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2020, 51(3): 221-238
doi: 10.11777/j.issn1000-3304.2019.19185
Abstract:
Over the past decade, besides fundamental concepts, single-crystal engineering of functional polymers and its applications have attracted increasing attention. With the advances of multiparametric and multifunctional characterization, atomic force microscopy (AFM) not only can image the surface topography of polymer crystals in nanoscale while simultaneously mapping the physical properties, like the electrical and thermal properties, but also provides a unique way of linking molecular structures, crystallization conditions and post-treatment to properties. Furthermore, the nanoscale control afforded by scanning probe lithography (SPL) has prompted the development of a regulation of the polymer aggregation structures and surface patterns in thin films. To explicitly probe the mechanism of polymer crystallization, single layer lamella and few layer lamellae in thin films as a model system, combined with AFM can provide information on polymer nucleation and growth with high spatial and temporal resolution. On the other hand, to promote a better understanding of the nature of heterogeneities of metastable state within the lamellae, lamellar thickening/melting and self-seeding, the effects of annealing temperature and time on lamellar thickness of metastable folded-chain crystals have been investigated in polymer thin films.
Over the past decade, besides fundamental concepts, single-crystal engineering of functional polymers and its applications have attracted increasing attention. With the advances of multiparametric and multifunctional characterization, atomic force microscopy (AFM) not only can image the surface topography of polymer crystals in nanoscale while simultaneously mapping the physical properties, like the electrical and thermal properties, but also provides a unique way of linking molecular structures, crystallization conditions and post-treatment to properties. Furthermore, the nanoscale control afforded by scanning probe lithography (SPL) has prompted the development of a regulation of the polymer aggregation structures and surface patterns in thin films. To explicitly probe the mechanism of polymer crystallization, single layer lamella and few layer lamellae in thin films as a model system, combined with AFM can provide information on polymer nucleation and growth with high spatial and temporal resolution. On the other hand, to promote a better understanding of the nature of heterogeneities of metastable state within the lamellae, lamellar thickening/melting and self-seeding, the effects of annealing temperature and time on lamellar thickness of metastable folded-chain crystals have been investigated in polymer thin films.
2020, 51(3): 239-266
doi: 10.11777/j.issn1000-3304.2019.19180
Abstract:
Sustainable polymers are a class of materials derived from renewable resources and exhibit closed-loop life cycles. The development of sustainable polymers has been an important research topic to meet the need of nonpetroleum-based materials and to reduce the dependence on fossil fuel over the past decades. Terpenes is a kind of natural products with extensive supply sources and has multiple reactive sites and chiral centers. They can be divided into cyclic monoterpenes, linear monoterpenes and polycyclic terpenes according to the number of isoprene units and skeleton ring in their molecular structures. Such structural characteristic can not only simplify the synthesis of sustainable polymers, but also be used to design sustainable polymers with accurate structure at the molecular level according to a variety of demands. Moreover, natural terpenes can endow sustainable polymers with unique stereochemical structures, good biological activity and biocompatibility, thus broadening their applications in surface coating, biological medicine, and tissue engineering. From the perspective of structural design, there are three main ways to construct natural terpene-based sustainable polymers: (1) main-chain sustainable polymers can be obtained by self-condensation polymerization or co-condensation of terpenes or their derivatives; (2) side-chain sustainable polymers can be obtained by homopolymerization or copolymerization of terpenes with unsaturated functional groups or terpene monomers modified by unsaturated moieties; (3) sustainable polymers end-capped with terpenes can be obtained by modifying the polymer chain end with terpenes or their derivatives. It should be noted that the structure discrepancy between natural terpenes may require different design strategies to create functional sustainable polymers. This paper reviews the progress of natural terpene-based sustainable polymers in recent decades in the order of cyclic monoterpenes, linear monoterpenes and polycyclic terpenes. The main resources, monomer design strategies and polymerization methods of natural terpenes, as well as the characteristics, advantages and potential applications of natural terpene-based sustainable polymers are discussed.
Sustainable polymers are a class of materials derived from renewable resources and exhibit closed-loop life cycles. The development of sustainable polymers has been an important research topic to meet the need of nonpetroleum-based materials and to reduce the dependence on fossil fuel over the past decades. Terpenes is a kind of natural products with extensive supply sources and has multiple reactive sites and chiral centers. They can be divided into cyclic monoterpenes, linear monoterpenes and polycyclic terpenes according to the number of isoprene units and skeleton ring in their molecular structures. Such structural characteristic can not only simplify the synthesis of sustainable polymers, but also be used to design sustainable polymers with accurate structure at the molecular level according to a variety of demands. Moreover, natural terpenes can endow sustainable polymers with unique stereochemical structures, good biological activity and biocompatibility, thus broadening their applications in surface coating, biological medicine, and tissue engineering. From the perspective of structural design, there are three main ways to construct natural terpene-based sustainable polymers: (1) main-chain sustainable polymers can be obtained by self-condensation polymerization or co-condensation of terpenes or their derivatives; (2) side-chain sustainable polymers can be obtained by homopolymerization or copolymerization of terpenes with unsaturated functional groups or terpene monomers modified by unsaturated moieties; (3) sustainable polymers end-capped with terpenes can be obtained by modifying the polymer chain end with terpenes or their derivatives. It should be noted that the structure discrepancy between natural terpenes may require different design strategies to create functional sustainable polymers. This paper reviews the progress of natural terpene-based sustainable polymers in recent decades in the order of cyclic monoterpenes, linear monoterpenes and polycyclic terpenes. The main resources, monomer design strategies and polymerization methods of natural terpenes, as well as the characteristics, advantages and potential applications of natural terpene-based sustainable polymers are discussed.
2020, 51(3): 267-276
doi: 10.11777/j.issn1000-3304.2019.19177
Abstract:
A series of main-chain azobenzene liquid crystalline copolyesters containing side hydroxyl group (Az-LCP) were synthesized with 4,4'-bis(6-hydroxyhexyloxy)biphenyl (BHHBP), 4,4'-bis(6-hydroxyhexyloxy)azobenzene (BHHAB), diethyl malate (DM) and phenyl succinic acid (PSA) by random copolymerization. Chemical structure of the Az-LCPs was characterized by proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). And the phase transition behavior of the Az-LCPs was characterized by differential scanning calorimeter (DSC), and X-ray diffraction (XRD). Az-LCPs showed a nematic phase with a glass transition temperature (Tg) around room temperature. With increasing BHHAB monomer, the Tg and nematic-isotropic transition temperature of Az-LCPs decreased from 25.6 °C and 96.4 °C to 19 °C and 88.2 °C, respectively, showing a trans-cis photoisomerization effect of Az-LCPs. Then monodomain azobenzene liquid crystalline networks (Az-LCNs) were prepared by uniaxial stretching at nematic phase first, postcrosslinking in the hexamethylene diisocyanate solution for 12 h. Moreover, the orientation degree decreased with increasing BHHAB monomer into Az-LCP due to the decreasing Tg and π-π stacking interaction. While being crosslinked with HDI, the Tg of Az-LCNs increased up to 40 °C, meanwhile, the nematic-isotropic phase transition became broad and almost disappeared as the BHHAB monomer increased. All the Az-LCNs showed a UV-light induced bending and vis-light induced unbending behavior at room temperature except Az-LCN4 which contains 50% BHHAB monomer. Crosslinking duration of Az-LCNs also exhibited an influence on the photoresponsive bending/unbending behavior. With increasing crosslinking duration, the bending angle increased first and then decreased. In addition, the maximum bending angle and photoresponsive speed of Az-LCNs decreased with increasing thickness of the Az-LCNs films. Az-LCP1 with 10% azobenzene content and cross-linking for 12 h exhibits excellent photoresponsive behavior with a high bending angle of 88° and the fastest photoresponsive speed.
A series of main-chain azobenzene liquid crystalline copolyesters containing side hydroxyl group (Az-LCP) were synthesized with 4,4'-bis(6-hydroxyhexyloxy)biphenyl (BHHBP), 4,4'-bis(6-hydroxyhexyloxy)azobenzene (BHHAB), diethyl malate (DM) and phenyl succinic acid (PSA) by random copolymerization. Chemical structure of the Az-LCPs was characterized by proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). And the phase transition behavior of the Az-LCPs was characterized by differential scanning calorimeter (DSC), and X-ray diffraction (XRD). Az-LCPs showed a nematic phase with a glass transition temperature (Tg) around room temperature. With increasing BHHAB monomer, the Tg and nematic-isotropic transition temperature of Az-LCPs decreased from 25.6 °C and 96.4 °C to 19 °C and 88.2 °C, respectively, showing a trans-cis photoisomerization effect of Az-LCPs. Then monodomain azobenzene liquid crystalline networks (Az-LCNs) were prepared by uniaxial stretching at nematic phase first, postcrosslinking in the hexamethylene diisocyanate solution for 12 h. Moreover, the orientation degree decreased with increasing BHHAB monomer into Az-LCP due to the decreasing Tg and π-π stacking interaction. While being crosslinked with HDI, the Tg of Az-LCNs increased up to 40 °C, meanwhile, the nematic-isotropic phase transition became broad and almost disappeared as the BHHAB monomer increased. All the Az-LCNs showed a UV-light induced bending and vis-light induced unbending behavior at room temperature except Az-LCN4 which contains 50% BHHAB monomer. Crosslinking duration of Az-LCNs also exhibited an influence on the photoresponsive bending/unbending behavior. With increasing crosslinking duration, the bending angle increased first and then decreased. In addition, the maximum bending angle and photoresponsive speed of Az-LCNs decreased with increasing thickness of the Az-LCNs films. Az-LCP1 with 10% azobenzene content and cross-linking for 12 h exhibits excellent photoresponsive behavior with a high bending angle of 88° and the fastest photoresponsive speed.
2020, 51(3): 277-286
doi: 10.11777/j.issn1000-3304.2019.19171
Abstract:
The carboxyl-terminated polydiene is a kind of widely used telechelic liquid rubber, which is commonly used as adhesive for solid rocket propellant, material bonding, sealant, electric insulation or as modifier of epoxy resins. Taking diene rubbers as raw materials, the carboxyl-terminated polydienes were synthesized via olefin metathesis degradation of diene rubbers catalyzed by Grubbs II catalyst ( G2 ) in the presence of maleic acid as a chain transfer agent (CTA). The carboxyl-terminated polyolefins were further prepared by the subsequent chemical hydrogenation with p-toluenesulfonyl hydrazide/tri(n-propyl)amine reagents. The influences of reaction conditions on the molecular weight and molecular weight distribution of products, including reaction time, reaction temperature, molar ratios of C＝C/catalyst and C＝C/chain transfer agent, were investigated. The results indicated that the molecular weight of products could be controlled by varying the molar ratio of C＝C/catalyst or C＝C/chain transfer agent. It turned out that the catalyst was highly active for the metathesis degradation of diene rubbers even if there was no existence of chain transfer agents. The structures of carboxyl-terminated polydienes and polyolefins were characterized by nuclear magnetic resonance spectroscopy (1H-NMR) and carbon spectrum (13C-NMR), infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It’s worth noting that the trans-1,4 content of carboxyl-terminated polybutadiene via metathesis degradation greatly increased and the corresponding cis-1,4 content decreased, thus affecting the properties of polymers. After hydrogenation, the carboxyl-terminated polyolefins had better thermal stability than the carboxyl-terminated polydienes.
The carboxyl-terminated polydiene is a kind of widely used telechelic liquid rubber, which is commonly used as adhesive for solid rocket propellant, material bonding, sealant, electric insulation or as modifier of epoxy resins. Taking diene rubbers as raw materials, the carboxyl-terminated polydienes were synthesized via olefin metathesis degradation of diene rubbers catalyzed by Grubbs II catalyst ( G2 ) in the presence of maleic acid as a chain transfer agent (CTA). The carboxyl-terminated polyolefins were further prepared by the subsequent chemical hydrogenation with p-toluenesulfonyl hydrazide/tri(n-propyl)amine reagents. The influences of reaction conditions on the molecular weight and molecular weight distribution of products, including reaction time, reaction temperature, molar ratios of C＝C/catalyst and C＝C/chain transfer agent, were investigated. The results indicated that the molecular weight of products could be controlled by varying the molar ratio of C＝C/catalyst or C＝C/chain transfer agent. It turned out that the catalyst was highly active for the metathesis degradation of diene rubbers even if there was no existence of chain transfer agents. The structures of carboxyl-terminated polydienes and polyolefins were characterized by nuclear magnetic resonance spectroscopy (1H-NMR) and carbon spectrum (13C-NMR), infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It’s worth noting that the trans-1,4 content of carboxyl-terminated polybutadiene via metathesis degradation greatly increased and the corresponding cis-1,4 content decreased, thus affecting the properties of polymers. After hydrogenation, the carboxyl-terminated polyolefins had better thermal stability than the carboxyl-terminated polydienes.
2020, 51(3): 287-294
doi: 10.11777/j.issn1000-3304.2019.19172
Abstract:
In recent years, research on interface modification based on dopamine has been greatly developed, but the high price of dopamine limits its practical application. Cheap catechol-tetraethylenepentamine (Cat-TEPA), similar to dopamine, can spontaneously polymerize and then deposit on the surface of various materials, exhibiting strong adhesion, reactivity, and no selectivity to the substrate. Surface modification based on Cat-TEPA has become a universal method suitable for practical applications. In this paper, ultra-high molecular weight polyethylene (UHMWPE) fiber was modified by Cat-TEPA. Transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the static contact angle investigations were used to characterize the structure and performance of the modified fibers. The interfacial shear strength (IFSS) between the fiber and the epoxy resin before and after modification was measured by monofilament extraction experiment. The effects of reactant ratio and reaction time on interface properties were explored and the optimal modification conditions were determined. The results show that Cat-TEPA modification does not affect the crystallization and thermal stability of the fiber, and the surface wettability of the fiber is improved after modification. An optimal IFSS increase of about 44% has been obtained when the molar ratio of Cat-TEPA is 1:4 and reaction time is 24 h.
In recent years, research on interface modification based on dopamine has been greatly developed, but the high price of dopamine limits its practical application. Cheap catechol-tetraethylenepentamine (Cat-TEPA), similar to dopamine, can spontaneously polymerize and then deposit on the surface of various materials, exhibiting strong adhesion, reactivity, and no selectivity to the substrate. Surface modification based on Cat-TEPA has become a universal method suitable for practical applications. In this paper, ultra-high molecular weight polyethylene (UHMWPE) fiber was modified by Cat-TEPA. Transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the static contact angle investigations were used to characterize the structure and performance of the modified fibers. The interfacial shear strength (IFSS) between the fiber and the epoxy resin before and after modification was measured by monofilament extraction experiment. The effects of reactant ratio and reaction time on interface properties were explored and the optimal modification conditions were determined. The results show that Cat-TEPA modification does not affect the crystallization and thermal stability of the fiber, and the surface wettability of the fiber is improved after modification. An optimal IFSS increase of about 44% has been obtained when the molar ratio of Cat-TEPA is 1:4 and reaction time is 24 h.
2020, 51(3): 295-302
doi: 10.11777/j.issn1000-3304.2019.19164
Abstract:
Increasing demands to improve the energy storage density of polymer dielectric materials have spurred the development of polymers with enhanced permittivity and improved dielectric breakdown. The introduction of high permittivity fillers can effectively improve the polymer permittivity, but it is also easy to cause the reduction of breakdown strength, which affected the improvement of the energy storage density of polymer materials. In this study, the polyimide-based nanocomposite films were fabricated via the in situ polymerization with high permittivity barium titanate (BT) nanoparticles and two-dimensional nanosheets exfoliatred from hydrotalcite (HT) as fillers . The permittivity of PI/BT films gradually increased with the increaseing content of BT nanoparticles. However, the breakdown strength decreased significantly with the increase of BT content. Therefore, the energy storage density of PI/BT composite films showed a remarkable decrease. However, with a small amount of two-dimensional nanosheets of hydrotalcite adding to the PI/BT composite films, the breakdown strength of the composites showed an obvious increase trend. The breakdown strength of the PI/BT film conntaining 30% BT increased by 32.8% when only 1% two-dimensional nanosheets were added. The improvement effect of two-dimensional nanometer sheet on the breakdown strength of PI/BT composite material is the same under different BT contents. Therefore, the penetration strength of PI/BT composite film can be effectively improved by adding two-dimensional nanocrystalline sheets, thus increasing the energy storage density. This is due to the fact that two-dimensional nanosheets can effectively improve the dispersion of high content nanoparticles in the polymer matrix, thus improving the properties of composites related to the dispersion of nanoparticles. Experimental results showed that by introducing two different morphology fillers, the permittivity and breakdown strength of PI/BT/HT composite films can be improved. With the addition of 20% BT and 1% HT, the energy storage density of PI/BT/HT composite film can reach 2.58 J/cm3, which is 14.6% higher than that of the composite film with only 20% BT. This method of simultaneously adding two different morphology fillers such as nano particles and two-dimensional nanosheets into the polymer matrix was expected to be applied in more fields of nanocomposite materials, especially in fields with high content of nano particles.
Increasing demands to improve the energy storage density of polymer dielectric materials have spurred the development of polymers with enhanced permittivity and improved dielectric breakdown. The introduction of high permittivity fillers can effectively improve the polymer permittivity, but it is also easy to cause the reduction of breakdown strength, which affected the improvement of the energy storage density of polymer materials. In this study, the polyimide-based nanocomposite films were fabricated via the in situ polymerization with high permittivity barium titanate (BT) nanoparticles and two-dimensional nanosheets exfoliatred from hydrotalcite (HT) as fillers . The permittivity of PI/BT films gradually increased with the increaseing content of BT nanoparticles. However, the breakdown strength decreased significantly with the increase of BT content. Therefore, the energy storage density of PI/BT composite films showed a remarkable decrease. However, with a small amount of two-dimensional nanosheets of hydrotalcite adding to the PI/BT composite films, the breakdown strength of the composites showed an obvious increase trend. The breakdown strength of the PI/BT film conntaining 30% BT increased by 32.8% when only 1% two-dimensional nanosheets were added. The improvement effect of two-dimensional nanometer sheet on the breakdown strength of PI/BT composite material is the same under different BT contents. Therefore, the penetration strength of PI/BT composite film can be effectively improved by adding two-dimensional nanocrystalline sheets, thus increasing the energy storage density. This is due to the fact that two-dimensional nanosheets can effectively improve the dispersion of high content nanoparticles in the polymer matrix, thus improving the properties of composites related to the dispersion of nanoparticles. Experimental results showed that by introducing two different morphology fillers, the permittivity and breakdown strength of PI/BT/HT composite films can be improved. With the addition of 20% BT and 1% HT, the energy storage density of PI/BT/HT composite film can reach 2.58 J/cm3, which is 14.6% higher than that of the composite film with only 20% BT. This method of simultaneously adding two different morphology fillers such as nano particles and two-dimensional nanosheets into the polymer matrix was expected to be applied in more fields of nanocomposite materials, especially in fields with high content of nano particles.
2020, 51(3): 303-310
doi: 10.11777/j.issn1000-3304.2019.19167
Abstract:
Aiming at the demands for recyclable resins and composites in practical applications, high performance recyclable epoxy resins with excellent comprehensive properties are prepared using methyl teterahydrophthalic anhydride as the curing agent and zinc acetylacetonate hydrate as the catalyst. The effects of anhydride and catalyst concentrations on the structure, thermal and dynamic properties of epoxy vitrimers are systematically explored to achieve the resin formulation optimization. With the decrease of anhydride concentrations, the cross-linking densities decrease, and the epoxy vitrimers show decreased glass transition temperature (Tg) but enhanced dynamic properties, which is attributed to the sufficient hydroxyl groups in structure that could trigger the transesterification exchange reactions with ester bonds. The increase of catalyst concentrations can also lead to enhanced dynamic properties as a result of the accelerated transesterification rates. The epoxy vitrimer with epoxy/anhydride/catalyst ratios of 1:0.5:0.05 displays optimal comprehensive performance with intermediate thermal properties and excellent dynamic properties. Based on the dynamic transesterification reaction, the epoxy vitrimers can be well reprocessed by the physically hot pressing methods at 180 °C for 6 h under a pressure of 10 MPa, and the recycling efficiency can be up to 80%. Moreover, the epoxy vitrimer-based carbon fiber reinforced composites are prepared by the resin transfer molding (RTM) technique. The prepared carbon fabric composites show a tensile strength of 479 MPa and tensile modulus of 58 GPa, revealing comparable mechanical properties to those of traditional thermoset composites. After heating the composites in ethylene glycol solvent at 180 °C for 8 h, the clean carbon fiber fabric with the same dimension as fresh ones can be reclaimed due to the dissolution of epoxy vitrimer binder in alcohol solvent via transesterification. In addition, the collected dissolved polymers can form vitrimers again by evaporating the EG solvent in open air at 180 °C for 12 h. It is demonstrated that the carbon fibers and epoxy polymers can both be fully recycled from the composites by the alcohol solvent dissolution method.
Aiming at the demands for recyclable resins and composites in practical applications, high performance recyclable epoxy resins with excellent comprehensive properties are prepared using methyl teterahydrophthalic anhydride as the curing agent and zinc acetylacetonate hydrate as the catalyst. The effects of anhydride and catalyst concentrations on the structure, thermal and dynamic properties of epoxy vitrimers are systematically explored to achieve the resin formulation optimization. With the decrease of anhydride concentrations, the cross-linking densities decrease, and the epoxy vitrimers show decreased glass transition temperature (Tg) but enhanced dynamic properties, which is attributed to the sufficient hydroxyl groups in structure that could trigger the transesterification exchange reactions with ester bonds. The increase of catalyst concentrations can also lead to enhanced dynamic properties as a result of the accelerated transesterification rates. The epoxy vitrimer with epoxy/anhydride/catalyst ratios of 1:0.5:0.05 displays optimal comprehensive performance with intermediate thermal properties and excellent dynamic properties. Based on the dynamic transesterification reaction, the epoxy vitrimers can be well reprocessed by the physically hot pressing methods at 180 °C for 6 h under a pressure of 10 MPa, and the recycling efficiency can be up to 80%. Moreover, the epoxy vitrimer-based carbon fiber reinforced composites are prepared by the resin transfer molding (RTM) technique. The prepared carbon fabric composites show a tensile strength of 479 MPa and tensile modulus of 58 GPa, revealing comparable mechanical properties to those of traditional thermoset composites. After heating the composites in ethylene glycol solvent at 180 °C for 8 h, the clean carbon fiber fabric with the same dimension as fresh ones can be reclaimed due to the dissolution of epoxy vitrimer binder in alcohol solvent via transesterification. In addition, the collected dissolved polymers can form vitrimers again by evaporating the EG solvent in open air at 180 °C for 12 h. It is demonstrated that the carbon fibers and epoxy polymers can both be fully recycled from the composites by the alcohol solvent dissolution method.
2020, 51(3): 311-318
doi: 10.11777/j.issn1000-3304.2019.19173
Abstract:
It has become a very mature and effective method to construct complex nanostructures by the self-assembly of amphiphilic block copolymer in solution or in bulk. A large number of studies have been reported that the assembly morphology of amphiphilic block copolymer can be accurately controlled by adjusting the block ratio, concentration, block compatibility and solvent conditions. Meanwhile, compared with the solution self-assembly method, the combination of substrate restriction and solvent annealing provides another way for the construction and regulation of complex nanostructures. However, due to the limitations of experimental methods, two basic problems have not been resolved. The first one is that, after the solvent selectivity was changed, the structural transformation dynamics of micelle were not clear. The second one is that, the current studies are only limited to the structural transformation process of spherical micelles in different solvents, the structural evolution kinetics of other shaped micelles or vesicles in the reverse solvent or at interface have not been reported. Thus, it is necessary to address these issues through computer simulation. In this paper, the transformation dynamics of diblock copolymers assemblies in reverse selective solvent were disclosed using dissipative particle dynamics simulation. Simulation results show that after the change of solvent selectivity, the large spherical micelles were respectively transformed into the reverse spherical micelle in solution and the ring-like micelle at the interface. The simulation results were in agreement with the available experimental result. In addition, the simulation results also predicted that after the change of solvent selectivity, the ring-like micelle, the wormlike micelle and the vesicle were transformed into the reverse ring-like micelle, the reverse ring-like micelle and multimicelle aggregate in solution, respectively, while they were transformed into the branched wormlike micelle, the multilayer nanoparticle and the patch nanoparticle at the interface, respectively. The current work provide important guidance for the design and preparation of novel nanostructures.
It has become a very mature and effective method to construct complex nanostructures by the self-assembly of amphiphilic block copolymer in solution or in bulk. A large number of studies have been reported that the assembly morphology of amphiphilic block copolymer can be accurately controlled by adjusting the block ratio, concentration, block compatibility and solvent conditions. Meanwhile, compared with the solution self-assembly method, the combination of substrate restriction and solvent annealing provides another way for the construction and regulation of complex nanostructures. However, due to the limitations of experimental methods, two basic problems have not been resolved. The first one is that, after the solvent selectivity was changed, the structural transformation dynamics of micelle were not clear. The second one is that, the current studies are only limited to the structural transformation process of spherical micelles in different solvents, the structural evolution kinetics of other shaped micelles or vesicles in the reverse solvent or at interface have not been reported. Thus, it is necessary to address these issues through computer simulation. In this paper, the transformation dynamics of diblock copolymers assemblies in reverse selective solvent were disclosed using dissipative particle dynamics simulation. Simulation results show that after the change of solvent selectivity, the large spherical micelles were respectively transformed into the reverse spherical micelle in solution and the ring-like micelle at the interface. The simulation results were in agreement with the available experimental result. In addition, the simulation results also predicted that after the change of solvent selectivity, the ring-like micelle, the wormlike micelle and the vesicle were transformed into the reverse ring-like micelle, the reverse ring-like micelle and multimicelle aggregate in solution, respectively, while they were transformed into the branched wormlike micelle, the multilayer nanoparticle and the patch nanoparticle at the interface, respectively. The current work provide important guidance for the design and preparation of novel nanostructures.
