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2015 Volume 33 Issue 4
2015, 33(4): 523-539
doi: 10.1007/s10118-015-1601-7
Abstract:
We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, and decrease its level of mathematical complexity. We report a novel method that allows us to solve one of the two equations of the model exactly, thus putting the level of mathematical difficulty on a par with the one of other models for polymer fluids. Moreover, we describe a computational algorithm capable of fitting all five parameters of the model in an unbiased way. The results obtained reproduce literature results and fit experimental pressure-volume-temperature and solubility parameter data for three polymers very accurately. Moreover, the new techniques allow for the investigation of the model at very low temperatures. Unexpectedly, the model predicts behaviors that could be interpreted as a glass transition, as routinely observed in dilatometry and differential scanning calorimetry, and a glass phase. We compared the predicted and experimental Tg's for cis poly(1,4-butadiene) and found an excellent quantitative agreement.
We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, and decrease its level of mathematical complexity. We report a novel method that allows us to solve one of the two equations of the model exactly, thus putting the level of mathematical difficulty on a par with the one of other models for polymer fluids. Moreover, we describe a computational algorithm capable of fitting all five parameters of the model in an unbiased way. The results obtained reproduce literature results and fit experimental pressure-volume-temperature and solubility parameter data for three polymers very accurately. Moreover, the new techniques allow for the investigation of the model at very low temperatures. Unexpectedly, the model predicts behaviors that could be interpreted as a glass transition, as routinely observed in dilatometry and differential scanning calorimetry, and a glass phase. We compared the predicted and experimental Tg's for cis poly(1,4-butadiene) and found an excellent quantitative agreement.
2015, 33(4): 540-553
doi: 10.1007/s10118-015-1605-3
Abstract:
A kind of amphiphilic functional monomer was selected to modify polyacrylamide (PAM) or partially hydrolyzed polyacrylamide (HPAM). The relative properties of the modified polyacrylamide (HM-PAM) and modified partially hydrolyzed polyacrylamide (HM-HPAM) such as radius of gyration (Rg), hydrodynamic radius (RH), and radial distribution functions (RDFs) have been studied to find the intrinsic relation between the microstructure of the polymer chain and the intrinsic viscosities with changing the amount of modified monomers from 1% to 4%. The simulation results show that, compared to HPAM, HM-HPAM has a better performance in increasing viscosity when the percentage of modified monomers is 2% and has a stronger salt tolerance when the modified monomers is 4%. Furthermore, a complex hydrogen bonding network was revealed with the analysis of radial distribution functions (RDFs) and the pair correlation function was used to investigate the diffusivity of Na+ and carbon atoms in the COO- group.
A kind of amphiphilic functional monomer was selected to modify polyacrylamide (PAM) or partially hydrolyzed polyacrylamide (HPAM). The relative properties of the modified polyacrylamide (HM-PAM) and modified partially hydrolyzed polyacrylamide (HM-HPAM) such as radius of gyration (Rg), hydrodynamic radius (RH), and radial distribution functions (RDFs) have been studied to find the intrinsic relation between the microstructure of the polymer chain and the intrinsic viscosities with changing the amount of modified monomers from 1% to 4%. The simulation results show that, compared to HPAM, HM-HPAM has a better performance in increasing viscosity when the percentage of modified monomers is 2% and has a stronger salt tolerance when the modified monomers is 4%. Furthermore, a complex hydrogen bonding network was revealed with the analysis of radial distribution functions (RDFs) and the pair correlation function was used to investigate the diffusivity of Na+ and carbon atoms in the COO- group.
2015, 33(4): 554-563
doi: 10.1007/s10118-015-1606-2
Abstract:
Nano-SiO2 and/or MoO3 were introduced to ethylene-vinyl acetate/nitrile butadiene rubber (EVA/NBR) blends containing magnesium hydroxide (MH) and red phosphorus (RP) to further improve the mechanical properties, oil resistance, smoke suppression and flame retardancy. The results indicated that the tensile strength and oil resistance were significantly improved by incorporating nano-SiO2. Smoke suppression tests for EVA/NBR blend samples showed that both nano-SiO2 and MoO3 can significantly reduce smoke release amount. The flammability characterization indicated that the blended sample with an LOI value of 33.0 could achieve V-0 level in the UL-94 test. Cone calorimetry test data showed the peak heat release rate was 67% lower than that for pure EVA/NBR. Thermal analysis showed that the presence of both nano-SiO2 and MoO3 was beneficial to promoting char formation of the EVA/NBR blends. Char residual analysis suggested that MoO3 aggregated in solid phase during combustion.
Nano-SiO2 and/or MoO3 were introduced to ethylene-vinyl acetate/nitrile butadiene rubber (EVA/NBR) blends containing magnesium hydroxide (MH) and red phosphorus (RP) to further improve the mechanical properties, oil resistance, smoke suppression and flame retardancy. The results indicated that the tensile strength and oil resistance were significantly improved by incorporating nano-SiO2. Smoke suppression tests for EVA/NBR blend samples showed that both nano-SiO2 and MoO3 can significantly reduce smoke release amount. The flammability characterization indicated that the blended sample with an LOI value of 33.0 could achieve V-0 level in the UL-94 test. Cone calorimetry test data showed the peak heat release rate was 67% lower than that for pure EVA/NBR. Thermal analysis showed that the presence of both nano-SiO2 and MoO3 was beneficial to promoting char formation of the EVA/NBR blends. Char residual analysis suggested that MoO3 aggregated in solid phase during combustion.
2015, 33(4): 564-575
doi: 10.1007/s10118-015-1607-1
Abstract:
A non-aqueous suspension polycondensation method was proposed to proceed the reaction of p-phenylenediamine and terephthaloyl chloride for the preparation of poly(p-phenylene terephthalamide) (PPTA). The system was operated with NMP-CaCl2 solution as the dispersed phase and inert liquid paraffin as the continuous phase. Each of NMP-CaCl2 solution microdroplet suspended in paraffin served as a microreactor where the polycondensation took place. According to the results of TGA, XRD, IR, SEM and EA, PPTA with good quality was obtained through this novel method, and a number of main factors influencing this process were investigated to determine the optimum condition for the preparation of PPTA. Besides, this two-phase polycondensation system brings many unique advantages compared to the conventional solution polycondensation method, including a sealed reaction environment keeping the reactants away from oxygen and water, easy removal of HCl to promote the reaction, well-controlled temperature and low viscosity which means less energy cost.
A non-aqueous suspension polycondensation method was proposed to proceed the reaction of p-phenylenediamine and terephthaloyl chloride for the preparation of poly(p-phenylene terephthalamide) (PPTA). The system was operated with NMP-CaCl2 solution as the dispersed phase and inert liquid paraffin as the continuous phase. Each of NMP-CaCl2 solution microdroplet suspended in paraffin served as a microreactor where the polycondensation took place. According to the results of TGA, XRD, IR, SEM and EA, PPTA with good quality was obtained through this novel method, and a number of main factors influencing this process were investigated to determine the optimum condition for the preparation of PPTA. Besides, this two-phase polycondensation system brings many unique advantages compared to the conventional solution polycondensation method, including a sealed reaction environment keeping the reactants away from oxygen and water, easy removal of HCl to promote the reaction, well-controlled temperature and low viscosity which means less energy cost.
2015, 33(4): 576-586
doi: 10.1007/s10118-015-1608-0
Abstract:
The crystallization behavior of poly(butylene succinate) (PBS) nanocomposites with a wide range of contents of clays was revealed. It was of interest to find that the crystallization rate of PBS was accelerated obviously at relatively low contents of clays; while a retarded crystallization kinetics and a decreased crystallinity of PBS were found in the nanocomposites with higher clay contents. Two interplaying effects existed in the nanocomposites, i.e., a suppression effect of clays on nucleation and a templating effect of clays on crystal growth, were clarified to contribute to this intriguing crystallization behavior.
The crystallization behavior of poly(butylene succinate) (PBS) nanocomposites with a wide range of contents of clays was revealed. It was of interest to find that the crystallization rate of PBS was accelerated obviously at relatively low contents of clays; while a retarded crystallization kinetics and a decreased crystallinity of PBS were found in the nanocomposites with higher clay contents. Two interplaying effects existed in the nanocomposites, i.e., a suppression effect of clays on nucleation and a templating effect of clays on crystal growth, were clarified to contribute to this intriguing crystallization behavior.
2015, 33(4): 587-596
doi: 10.1007/s10118-015-1611-5
Abstract:
An electrospun poly(lactide-co-glycolide) (PLGA) membrane was prepared and used to perform the anti-adhesion of Achilles tendon. Throughout the experiments, the membrane showed an appropriate degradation rate, and the pH values of degradation media were maintained at around 7.4. Simultaneously, the excellent biocompatibility of the membrane in vitro and in vivo was confirmed by live/dead and histopathological analyses. Meanwhile, the membrane can reduce tendon adhesion significantly and promote functional recovery effectively. The encouraging results were further demonstrated by hematoxylin and eosin (HE), and Masson's trichrome stainings, and type I collagen immunohistochemical analysis. It was concluded that the model treated with the electrospun PLGA membrane was significantly better with respect to the adhesion prevention and tissue repair than that without treatment. Considering the results of degradation and adhesion prevention efficacy, the electrospun PLGA membrane would be a great candidate for the prevention of postoperative tendon adhesion.
An electrospun poly(lactide-co-glycolide) (PLGA) membrane was prepared and used to perform the anti-adhesion of Achilles tendon. Throughout the experiments, the membrane showed an appropriate degradation rate, and the pH values of degradation media were maintained at around 7.4. Simultaneously, the excellent biocompatibility of the membrane in vitro and in vivo was confirmed by live/dead and histopathological analyses. Meanwhile, the membrane can reduce tendon adhesion significantly and promote functional recovery effectively. The encouraging results were further demonstrated by hematoxylin and eosin (HE), and Masson's trichrome stainings, and type I collagen immunohistochemical analysis. It was concluded that the model treated with the electrospun PLGA membrane was significantly better with respect to the adhesion prevention and tissue repair than that without treatment. Considering the results of degradation and adhesion prevention efficacy, the electrospun PLGA membrane would be a great candidate for the prevention of postoperative tendon adhesion.
2015, 33(4): 597-606
doi: 10.1007/s10118-015-1610-6
Abstract:
To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer (PTP(E-co-T)) was prepared from hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer (P(E-co-T)) by end-etherisation modification. FTIR and 13C-NMR results indicate that P(E-co-T)-terminated hydroxyl was etherified thoroughly, yielding the target product PTP(E-co-T), and the content of terminated alkynyl of PTP(E-co-T) was evaluated to be 0.428 mmolg-1. Using a polyazide compound as a cross-linker, polytriazole elastomers with various functional molar ratio (R) values were prepared from PTP(E-co-T) by virtue of the CuAAC reaction. Mechanical property tests indicate that with the increase in R, the modulus E and stress b of the polytriazole elastomers first increase and subsequently decrease, whereas the strain first decreases and later increases. The mechanical properties of the polytriazole elastomers show a parabolic dependence on the R value. Near the stoichiometric ratio, E and b show maxima and the strain b shows a minimum. Swelling tests demonstrate that the apparent molecular weight of polytriazole elastomer strands also first decreases and subsequently increases. At the stoichiometric ratio, the network structure possesses strands with a minimum apparent molecular weight and a maximum apparent density. Dynamic mechanical analysis reveals that the polytriazole elastomers presented damping peaks at approximately -64 ℃, corresponding to the glass transition of copolyether strands, and the elastomer exhibited the lowest dissipation factor tan at the stoichiometric ratio. Thermal analysis suggests that the weight-loss process of the polytriazole elastomer is characteristic of one-step decomposition, and the elastomer begins to decompose from polyether strands, not triazole groups.
To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer (PTP(E-co-T)) was prepared from hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer (P(E-co-T)) by end-etherisation modification. FTIR and 13C-NMR results indicate that P(E-co-T)-terminated hydroxyl was etherified thoroughly, yielding the target product PTP(E-co-T), and the content of terminated alkynyl of PTP(E-co-T) was evaluated to be 0.428 mmolg-1. Using a polyazide compound as a cross-linker, polytriazole elastomers with various functional molar ratio (R) values were prepared from PTP(E-co-T) by virtue of the CuAAC reaction. Mechanical property tests indicate that with the increase in R, the modulus E and stress b of the polytriazole elastomers first increase and subsequently decrease, whereas the strain first decreases and later increases. The mechanical properties of the polytriazole elastomers show a parabolic dependence on the R value. Near the stoichiometric ratio, E and b show maxima and the strain b shows a minimum. Swelling tests demonstrate that the apparent molecular weight of polytriazole elastomer strands also first decreases and subsequently increases. At the stoichiometric ratio, the network structure possesses strands with a minimum apparent molecular weight and a maximum apparent density. Dynamic mechanical analysis reveals that the polytriazole elastomers presented damping peaks at approximately -64 ℃, corresponding to the glass transition of copolyether strands, and the elastomer exhibited the lowest dissipation factor tan at the stoichiometric ratio. Thermal analysis suggests that the weight-loss process of the polytriazole elastomer is characteristic of one-step decomposition, and the elastomer begins to decompose from polyether strands, not triazole groups.
Glass Transition Behavior of Spin-coated Thin Films of a Hydrophilic Polymer on Supported Substrates
2015, 33(4): 607-612
doi: 10.1007/s10118-015-1612-4
Abstract:
Using ellipsometry, it is found the glass transition temperature of the spin-coated polyacrylamide (PAL) thin films on the supported silicon (Si) substrates with an oxide layer decreases with decreasing the film thickness. But Tgs of the as-prepared thin films are much higher than that of the bulk sample. Such observations can be attributed to the combined result of the surface effect and increased hydrogen bonding interaction between PAL chains due to spin coating/thin film confinement.
Using ellipsometry, it is found the glass transition temperature of the spin-coated polyacrylamide (PAL) thin films on the supported silicon (Si) substrates with an oxide layer decreases with decreasing the film thickness. But Tgs of the as-prepared thin films are much higher than that of the bulk sample. Such observations can be attributed to the combined result of the surface effect and increased hydrogen bonding interaction between PAL chains due to spin coating/thin film confinement.
2015, 33(4): 613-620
doi: 10.1007/s10118-015-1613-3
Abstract:
On the basis of research method in FTIR imaging, we made a heterogeneous thin film of isotactic polypropylene (iPP) that contains a few large spherulites (~150 m) which are surrounded by small spherulites (~15 m) for tensile testing. The evolution processes of crystalline and amorphous orientations of iPP are monitored with its characteristic peaks at 998 and 973 cm-1, respectively. By introducing the correlation images, the analysis demonstrates the relationships between the orientation evolutions of crystalline and amorphous phases in a space of 250 m 250 m detecting area. During the plastic deformation, crystalline orientation is higher than amorphous orientation outside the large spherulite, while that is opposite inside the region. In addition, the evolutions of crystalline and amorphous orientations almost keep a positive correlation.
On the basis of research method in FTIR imaging, we made a heterogeneous thin film of isotactic polypropylene (iPP) that contains a few large spherulites (~150 m) which are surrounded by small spherulites (~15 m) for tensile testing. The evolution processes of crystalline and amorphous orientations of iPP are monitored with its characteristic peaks at 998 and 973 cm-1, respectively. By introducing the correlation images, the analysis demonstrates the relationships between the orientation evolutions of crystalline and amorphous phases in a space of 250 m 250 m detecting area. During the plastic deformation, crystalline orientation is higher than amorphous orientation outside the large spherulite, while that is opposite inside the region. In addition, the evolutions of crystalline and amorphous orientations almost keep a positive correlation.
2015, 33(4): 621-632
doi: 10.1007/s10118-015-1614-2
Abstract:
The effect of benzimidazole units on thermal imidizaiton was studied when they were introduced into the main chain of poly(amic acid) (PAA). The thermal imidization process of PAA-PABZ synthesized by 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2-(4-aminophenyl)-5(6)-aminobenzimidazole (PABZ) was studied by TGA, DSC, DMA, FTIR and in situ FTIR. The results of FTIR and in situ FTIR indicate benzimidazole units act as an in situ catalyst to accelerate thermal imidization of PAA to polyimide (PI) when the temperature is lower than 170 ℃. FTIR and 1H-NMR results demonstrate that in situ catalysis is caused by the hydrogen bonding interactions between C=N of benzimidazole and ―NH― in ―CONH― of PAA and the semi-ionization of the H in imidazole ring of benzimidazole. However, when the imidization temperature is higher than 170 ℃, the thermal imidization process is inhibited. DMA and in situ FTIR results illustrate that the decreased mobility of PI-PABZ macromolecular chains and the reduced reactive ability of anhydride formed during the intramolecular breakdown of polymer chains lead to the inhibition of thermal imidization process.
The effect of benzimidazole units on thermal imidizaiton was studied when they were introduced into the main chain of poly(amic acid) (PAA). The thermal imidization process of PAA-PABZ synthesized by 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2-(4-aminophenyl)-5(6)-aminobenzimidazole (PABZ) was studied by TGA, DSC, DMA, FTIR and in situ FTIR. The results of FTIR and in situ FTIR indicate benzimidazole units act as an in situ catalyst to accelerate thermal imidization of PAA to polyimide (PI) when the temperature is lower than 170 ℃. FTIR and 1H-NMR results demonstrate that in situ catalysis is caused by the hydrogen bonding interactions between C=N of benzimidazole and ―NH― in ―CONH― of PAA and the semi-ionization of the H in imidazole ring of benzimidazole. However, when the imidization temperature is higher than 170 ℃, the thermal imidization process is inhibited. DMA and in situ FTIR results illustrate that the decreased mobility of PI-PABZ macromolecular chains and the reduced reactive ability of anhydride formed during the intramolecular breakdown of polymer chains lead to the inhibition of thermal imidization process.
2015, 33(4): 633-645
doi: 10.1007/s10118-015-1616-0
Abstract:
We reported an approach to reconstruct the complex phase morphology of impact polypropylene copolymer (IPC) with core-shell dispersed particles and to optimize its toughness in approximate shear condition. The molten-state annealing results indicate that the phase structure with core-shell dispersed particles is unstable and could be completely destroyed by static annealing, resulting in the degradation of impact strength. By using a co-rotating twin screw extruder, we found that the dispersed particle with core-shell structure could be rebuilt in appropriate condition with the recovery of excellent impact strength due to both the huge interfacial tension during solidification and the great difference in viscosity of components. Results reveal that almost all the extruded IPCs show the impact strength 60%-90% higher than that of annealed IPCs at room temperature. And the twice-extruded IPC shows the highest impact strength, 446% higher than that of IPC annealed for 30 min. As for low temperature tests, the impact strength of extruded IPCs also increases by 33%-58%. According to adjusting the processing conditions including extrusion speed, extrusion frequency and temperature, an optimization of toughness was well established.
We reported an approach to reconstruct the complex phase morphology of impact polypropylene copolymer (IPC) with core-shell dispersed particles and to optimize its toughness in approximate shear condition. The molten-state annealing results indicate that the phase structure with core-shell dispersed particles is unstable and could be completely destroyed by static annealing, resulting in the degradation of impact strength. By using a co-rotating twin screw extruder, we found that the dispersed particle with core-shell structure could be rebuilt in appropriate condition with the recovery of excellent impact strength due to both the huge interfacial tension during solidification and the great difference in viscosity of components. Results reveal that almost all the extruded IPCs show the impact strength 60%-90% higher than that of annealed IPCs at room temperature. And the twice-extruded IPC shows the highest impact strength, 446% higher than that of IPC annealed for 30 min. As for low temperature tests, the impact strength of extruded IPCs also increases by 33%-58%. According to adjusting the processing conditions including extrusion speed, extrusion frequency and temperature, an optimization of toughness was well established.
2015, 33(4): 646-651
doi: 10.1007/s10118-015-1615-1
Abstract:
Herein we demonstrate crystallization-driven self-assembly of isotactic polystyrene (iPS) with high isotacticity and narrow molecular weight distribution and crystallization-induced switching of the morphology of iPS aggregates in N, N-dimethylformamide (DMF). The formation and morphology switching of the self-assembled aggregates of iPS are investigated by means of dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WXRD). The results reveal that cooling DMF solution of iPS promotes iPS chains to self-assemble into spherical aggregates with a gelled core cross-linked by microcrystals, which is surrounded by solvent-swollen corona. Furthermore, crystallization induces the deformation of iPS aggregates from spherical to plate-like or nest-like.
Herein we demonstrate crystallization-driven self-assembly of isotactic polystyrene (iPS) with high isotacticity and narrow molecular weight distribution and crystallization-induced switching of the morphology of iPS aggregates in N, N-dimethylformamide (DMF). The formation and morphology switching of the self-assembled aggregates of iPS are investigated by means of dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WXRD). The results reveal that cooling DMF solution of iPS promotes iPS chains to self-assemble into spherical aggregates with a gelled core cross-linked by microcrystals, which is surrounded by solvent-swollen corona. Furthermore, crystallization induces the deformation of iPS aggregates from spherical to plate-like or nest-like.
2015, 33(4): 652-660
doi: 10.1007/s10118-014-1475-0
Abstract:
The influences of hyperbranched polyethylenimine (hPEI), which possesses many reactive amino end-groups, on the blending properties of bisphenol-A polycarbonate (PC) and amorphous polyamide (aPA) were systematically investigated. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to observe the effect of hPEI on morphologies of PC and aPA phases in bulk blends. While the interfacial fracture toughness between planar PC and aPA layers with and without hPEI was studied by using augmented double cantilever beam (ADCB) method. Results show that the compatibility in PC/aPA blends can be significantly improved by adding a small amount of hPEI, mainly due to the interchange reactions between the polymers leading to the formation of block copolymers, cross-linked polymers and molecules with other constitutions. The augmented double cantilever beam experiments showed that the reactive process drastically reinforced the interfacial adhesion between planar layers of PC and aPA. However, degradation takes place during annealing at 180 ℃, which was responsible for the production of small molar mass species of PC.
The influences of hyperbranched polyethylenimine (hPEI), which possesses many reactive amino end-groups, on the blending properties of bisphenol-A polycarbonate (PC) and amorphous polyamide (aPA) were systematically investigated. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to observe the effect of hPEI on morphologies of PC and aPA phases in bulk blends. While the interfacial fracture toughness between planar PC and aPA layers with and without hPEI was studied by using augmented double cantilever beam (ADCB) method. Results show that the compatibility in PC/aPA blends can be significantly improved by adding a small amount of hPEI, mainly due to the interchange reactions between the polymers leading to the formation of block copolymers, cross-linked polymers and molecules with other constitutions. The augmented double cantilever beam experiments showed that the reactive process drastically reinforced the interfacial adhesion between planar layers of PC and aPA. However, degradation takes place during annealing at 180 ℃, which was responsible for the production of small molar mass species of PC.
2015, 33(4): 661-668
doi: 10.1007/s10118-015-1618-y
Abstract:
The asymmetric amphiphilic block copolymer polystyrene962-block-poly(ethylene oxide)227 (PS962-b-PEO227) canforms micelles with N, N-dimethylformamide (DMF) as co-solvent and water as selected solvent, and when the water content of the mixed solvent is higher than 4.5 wt%, the vesicle will be dominated. This work finds that once vesicles are formed in the DMF-water mixed solvent, the vesicle size and membrane thickness can be tuned by further increasing water content. As the water fraction elevated from 4.8 wt% to 13.0 wt%, the vesicle size dercreases from 246 nm to 150 nm, while the membrane thickness increases from 28 nm to 42 nm. In addition, the block copolymer packing and the free energy are analyzed as the vesicle size becomes small and the membrane becomes thick.
The asymmetric amphiphilic block copolymer polystyrene962-block-poly(ethylene oxide)227 (PS962-b-PEO227) canforms micelles with N, N-dimethylformamide (DMF) as co-solvent and water as selected solvent, and when the water content of the mixed solvent is higher than 4.5 wt%, the vesicle will be dominated. This work finds that once vesicles are formed in the DMF-water mixed solvent, the vesicle size and membrane thickness can be tuned by further increasing water content. As the water fraction elevated from 4.8 wt% to 13.0 wt%, the vesicle size dercreases from 246 nm to 150 nm, while the membrane thickness increases from 28 nm to 42 nm. In addition, the block copolymer packing and the free energy are analyzed as the vesicle size becomes small and the membrane becomes thick.
