The phase behavior of a well-defined poly(methyl methacrylate)- b- polystyrene block copolymer was studied by transmission electron microscope. The results show that a microphase transition may have occurred in the co...The phase behavior of a well-defined poly(methyl methacrylate)- b- polystyrene block copolymer was studied by transmission electron microscope. The results show that a microphase transition may have occurred in the copolymer film. A kind of lamellae and an ordered bicontinuous double-diamond morphology are observed clearly. The lamellar morphology reveals a larger period of about 400 nm.展开更多
High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as d...High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.展开更多
Bond fluctuation model and vacancy diffusion algorithm have been used to simulate the phase separation of AB block copolymer and blend in a highly concentrated system.The results are as follows:(i)The mixing is nonran...Bond fluctuation model and vacancy diffusion algorithm have been used to simulate the phase separation of AB block copolymer and blend in a highly concentrated system.The results are as follows:(i)The mixing is nonrandom even in athermal condition where the microscopic interaction energy between A and B monomersε~*=0,so that the assump. tion of random mixing in the mean-field theory is just a rough approximation.(ii)The Flory-Huggins(FH)parameter,X,is just a phenomenological parameter.Therefore,the X value of the block copolymer is higher than that of the corresponding blend although the reduced microscopic molecular interaction energies ε~* are the same.(iii)In the case of the same A,B composition and the same molecular weight of corresponding blocks,the phase separation of AB blend is easier than that of AB block copolymer.Their critical values of the X are:X_c^(blend)=0.1,X_c^(block)=0.41 for the case of chain lengths L_A=10,L_B=11.展开更多
Salt-doped block copolymers have widespread applications in batteries,fuel cells,semiconductors,and various industries,where their properties crucially depend on phase separation behavior.Traditionally,investigations ...Salt-doped block copolymers have widespread applications in batteries,fuel cells,semiconductors,and various industries,where their properties crucially depend on phase separation behavior.Traditionally,investigations into salt-doped diblock copolymers have predominantly focused on microphase separation,overlooking the segregation between ionic and polymeric species.This study employs weak segregation theory to explore the interplay between phase separation dominated by the polymer-modulated mode and the salt-out-modulated mode,corresponding to microscopic and macroscopic phase separations,respectively.By comparing diblock copolymers doped with salts to those doped with neutral solvents,we elucidate the significant role of charged species in modulating phase behavior.The phase separation mode exhibits a transition between the polymer-modulated and salt-out-modulated modes at different wavenumbers.In systems doped with neutral solvents,this transition is stepwise,while in salt-ion-doped systems,it is continuous.With a sufficiently large Flory-Huggins parameter between ions and polymers,the salt-out-modulated mode becomes dominant,promoting macrophase separation.Due to the solvation effect of salt ions,salt-doped systems are more inclined to undergo microphase separation.Furthermore,we explore factors influencing the critical wavenumber of phase separation,including doping level and the Flory-Huggins parameters between two blocks and between ions and polymeric species.Our findings reveal that in a neutral solvent environment,these factors alter only the boundary between micro-and macro-phase separations,leaving the critical wavenumber unchanged in microphase separation cases.However,in a salt-doped environment,the critical wavenumber of microphase separation varies with these parameters.This provides valuable insights into the pivotal role of electrostatics in the phase separation of salt-doped block copolymers.展开更多
Shape control of mesoporous carbon microparticles(MCMPs)is of critical importance;in particular,asymmetric shapes that can yield unique properties have attracted significant attention.However,the tailored synthesis of...Shape control of mesoporous carbon microparticles(MCMPs)is of critical importance;in particular,asymmetric shapes that can yield unique properties have attracted significant attention.However,the tailored synthesis of asymmetric MCMPs with ordered structures remains challenging.Herein,we report a facile route to prepare asymmetric MCMPs by dynamic neutral interface-guided 3D-confined self-assembly(3D-CSA)of block copolymer/homopolymer(BCP/hP)blends,followed by a self-templated selective direct carbonization strategy.BCP/h P Janus microparticles with ordered hierarchical mesostructures were prepared with emulsion solvent evaporation-induced 3D-CSA.The continuous phase of BCP domains was then crosslinked.Composite asymmetric MCMPs are successfully generated after selective carbonization of the crosslinked continuous phase.This method allows tuning the shape of MCMPs easily by varying the blending ratio of BCP/h P.The composite asymmetric MCMPs combine the advantages of asymmetric shape,ordered structure,high specific surface area,chemical inertness and thermal stability and could provide great possibilities for applications in catalysis,drug delivery,energy conversion and storage.展开更多
Amphiphilic diblock copolymers self-assemble into a variety of micellar structures with diverse shapes in selective solvents. Here, we study the concentration and temperature dependence of the packing structure of sph...Amphiphilic diblock copolymers self-assemble into a variety of micellar structures with diverse shapes in selective solvents. Here, we study the concentration and temperature dependence of the packing structure of spherical micelles of a polyisoprene-b-poly(2- vinylpyridine)(PI-b-P2VP) diblock copolymer in toluene using synchrotron radiation small angle X-ray scattering (SR-SAXS) and atomic force microscopy (AFM) techniques. Randomly packed spherical micelles are detected in dilute solutions, while in concentrated solutions, face-centered cubic (FCC), body-centered cubic (BCC) mixed crystal structures, and pure BCC crystal structures are observed with an increase in concentration. In situ SAXS experiments on the FCC/BCC mixed crystal structures reveal a novel FCC/BCC → BCC → Disorder → BCC phase behavior during the thermal annealing process. These results demonstrated that the BCC phase is apparently more stable than the FCC phase in the current sphere-packing system and FCC/BCC is a metastable state. The incompatibility of the PI and P2VP blocks decreases at a higher temperature and renders the variation of domain spacing.展开更多
In order to mimic hierarchical nanostructures in nature,particles of polymer blends consisting of poly(4-butyltriphenylamine)(PBTPA),poly(methyl methacrylate)(PMMA)and PBTPA-block-PMMA were fabricated by a solvent eva...In order to mimic hierarchical nanostructures in nature,particles of polymer blends consisting of poly(4-butyltriphenylamine)(PBTPA),poly(methyl methacrylate)(PMMA)and PBTPA-block-PMMA were fabricated by a solvent evaporation method.Effects of the molecular weight and the chemical composition of PBTPA-b-PMMA,molecular weights of homopolymers,and the composition of the blend on the morphology were investigated.The polymer blend particle consisting of PBTPA and PMMA homopolymers exhibited thermodynamically favored core-shell structure,in which more hydrophilic PMMA-shell surrounded PBTPA-core.The addition of 10 wt%of PBTPA-b-PMMA caused the morphological transition from core-shell toJanus or inversed core-shell,in which PBTPA-shell surrounded PMMA-core,depending on the molecular weight of PBTPA segment in PBTPA-b-PMMA.When the molecular weight of PMMA segment was higher than that of PMMA homopolymer,watermelon-like particles in which small PBTPA domain less than 80 nm dispersed in the PMMA domain surrounded by PBTPA shell were observed.As the ratio of PBTPA-b-PMMA increased,the interface of the macrophase separation became obscure.At 50 wt%of the PBTPA-b-PMMA,only microphase separation was observed.The measurement of interfacial tension by pendant drop method demonstrated that PBTPA-b-PMMA lower the interfacial tension between PBTPA and the aqueous phase to the value similar to that of PMMA with the aqueous phase.展开更多
Considering the inhomogeneity of the concentration distribution in the corona of a star\|shaped micelle, an equation system of free energy components was suggested in order to predict the micro\|phase separation of th...Considering the inhomogeneity of the concentration distribution in the corona of a star\|shaped micelle, an equation system of free energy components was suggested in order to predict the micro\|phase separation of the diblock copolymer in selective solvents. All energetic and entropic contributions to the free energy of micellization were included in equations for the micellar solution, which was composed of the di\|block copolymers with certain molecular weights and the solvent with special characters at a giving temperature. The minimization of free energy produced the equilibrium size and aggregation number of the micelle. The corona and core size of the micelle,the concentration profile of the soluble block in corona and the value of the aggregation number were obtained based on the present theory. Moreover, the theoretical predictions of the aggregation number were in good agreement with the experimental data for systems of polystyrene\|poly(2\|cinnamoylethyl methacrylate)/cyclopentane and poly(4\|vinylpyridine) \|polystyrene/toluene.展开更多
采用原子转移自由基聚合方法(A tom transfer rad ica l po lym erization,ATRP),以α-溴丙酸乙酯为引发剂,溴化亚铜和联二吡啶为催化体系,合成了端基为卤原子的单分散聚甲基丙烯酸甲酯(PMM A-X)预聚体。以此PMM A-X为大分子引发剂,在...采用原子转移自由基聚合方法(A tom transfer rad ica l po lym erization,ATRP),以α-溴丙酸乙酯为引发剂,溴化亚铜和联二吡啶为催化体系,合成了端基为卤原子的单分散聚甲基丙烯酸甲酯(PMM A-X)预聚体。以此PMM A-X为大分子引发剂,在同样催化体系下,引发苯乙烯聚合,得到了分子量分布较窄的聚甲基丙烯酸甲酯-b-聚苯乙烯(PMM A-b-PS t)嵌段共聚物,并用红外光谱(IR)、核磁共振谱(1H-NM R)、凝胶渗透色谱(GPC)和透射电子显微镜(TEM)对其结构和形态进行了初步表征。结果表明,嵌段共聚物中聚甲基丙烯酸甲酯的质量百分数为28%,数均分子量(M n)为4.76×104,多分散系数(PD I)为1.49。经TEM表征,发现该嵌段聚合物具有周期性层状相分离结构,层状取向周期达到了400 nm左右,在紫外-可见波长范围内。这一特征长周期为嵌段共聚物材料用作光波导等光学器件提供了结构基础。展开更多
文摘The phase behavior of a well-defined poly(methyl methacrylate)- b- polystyrene block copolymer was studied by transmission electron microscope. The results show that a microphase transition may have occurred in the copolymer film. A kind of lamellae and an ordered bicontinuous double-diamond morphology are observed clearly. The lamellar morphology reveals a larger period of about 400 nm.
基金supported by the 863 program(No.2006AA03Z233)973 program(No.2009CB623402) of China
文摘High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.
基金Project supported by the National Natural Science Foundation of China and Fok Ying Tung Education Foundation,State Education Commission of China.
文摘Bond fluctuation model and vacancy diffusion algorithm have been used to simulate the phase separation of AB block copolymer and blend in a highly concentrated system.The results are as follows:(i)The mixing is nonrandom even in athermal condition where the microscopic interaction energy between A and B monomersε~*=0,so that the assump. tion of random mixing in the mean-field theory is just a rough approximation.(ii)The Flory-Huggins(FH)parameter,X,is just a phenomenological parameter.Therefore,the X value of the block copolymer is higher than that of the corresponding blend although the reduced microscopic molecular interaction energies ε~* are the same.(iii)In the case of the same A,B composition and the same molecular weight of corresponding blocks,the phase separation of AB blend is easier than that of AB block copolymer.Their critical values of the X are:X_c^(blend)=0.1,X_c^(block)=0.41 for the case of chain lengths L_A=10,L_B=11.
基金supported by the Major Research Plan of the National Natural Science Foundation of China(No.92372104)Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110016)the Recruitment Program of Guangdong(No.2016ZT06C322),and TCL Science and Technology Innovation Fund.
文摘Salt-doped block copolymers have widespread applications in batteries,fuel cells,semiconductors,and various industries,where their properties crucially depend on phase separation behavior.Traditionally,investigations into salt-doped diblock copolymers have predominantly focused on microphase separation,overlooking the segregation between ionic and polymeric species.This study employs weak segregation theory to explore the interplay between phase separation dominated by the polymer-modulated mode and the salt-out-modulated mode,corresponding to microscopic and macroscopic phase separations,respectively.By comparing diblock copolymers doped with salts to those doped with neutral solvents,we elucidate the significant role of charged species in modulating phase behavior.The phase separation mode exhibits a transition between the polymer-modulated and salt-out-modulated modes at different wavenumbers.In systems doped with neutral solvents,this transition is stepwise,while in salt-ion-doped systems,it is continuous.With a sufficiently large Flory-Huggins parameter between ions and polymers,the salt-out-modulated mode becomes dominant,promoting macrophase separation.Due to the solvation effect of salt ions,salt-doped systems are more inclined to undergo microphase separation.Furthermore,we explore factors influencing the critical wavenumber of phase separation,including doping level and the Flory-Huggins parameters between two blocks and between ions and polymeric species.Our findings reveal that in a neutral solvent environment,these factors alter only the boundary between micro-and macro-phase separations,leaving the critical wavenumber unchanged in microphase separation cases.However,in a salt-doped environment,the critical wavenumber of microphase separation varies with these parameters.This provides valuable insights into the pivotal role of electrostatics in the phase separation of salt-doped block copolymers.
基金financially supported by the National Natural Science Foundation of China(Nos.52003094 and 52273010)。
文摘Shape control of mesoporous carbon microparticles(MCMPs)is of critical importance;in particular,asymmetric shapes that can yield unique properties have attracted significant attention.However,the tailored synthesis of asymmetric MCMPs with ordered structures remains challenging.Herein,we report a facile route to prepare asymmetric MCMPs by dynamic neutral interface-guided 3D-confined self-assembly(3D-CSA)of block copolymer/homopolymer(BCP/hP)blends,followed by a self-templated selective direct carbonization strategy.BCP/h P Janus microparticles with ordered hierarchical mesostructures were prepared with emulsion solvent evaporation-induced 3D-CSA.The continuous phase of BCP domains was then crosslinked.Composite asymmetric MCMPs are successfully generated after selective carbonization of the crosslinked continuous phase.This method allows tuning the shape of MCMPs easily by varying the blending ratio of BCP/h P.The composite asymmetric MCMPs combine the advantages of asymmetric shape,ordered structure,high specific surface area,chemical inertness and thermal stability and could provide great possibilities for applications in catalysis,drug delivery,energy conversion and storage.
基金financially supported by the National Natural Science Foundation of China (No. U1632117)the Shanghai Education Development Foundationthe Shanghai Municipal Education Commission (No. 16SG54)
文摘Amphiphilic diblock copolymers self-assemble into a variety of micellar structures with diverse shapes in selective solvents. Here, we study the concentration and temperature dependence of the packing structure of spherical micelles of a polyisoprene-b-poly(2- vinylpyridine)(PI-b-P2VP) diblock copolymer in toluene using synchrotron radiation small angle X-ray scattering (SR-SAXS) and atomic force microscopy (AFM) techniques. Randomly packed spherical micelles are detected in dilute solutions, while in concentrated solutions, face-centered cubic (FCC), body-centered cubic (BCC) mixed crystal structures, and pure BCC crystal structures are observed with an increase in concentration. In situ SAXS experiments on the FCC/BCC mixed crystal structures reveal a novel FCC/BCC → BCC → Disorder → BCC phase behavior during the thermal annealing process. These results demonstrated that the BCC phase is apparently more stable than the FCC phase in the current sphere-packing system and FCC/BCC is a metastable state. The incompatibility of the PI and P2VP blocks decreases at a higher temperature and renders the variation of domain spacing.
基金supported by Institute of Global Innovation Research in Tokyo University of Agriculture and Technology(TUAT).
文摘In order to mimic hierarchical nanostructures in nature,particles of polymer blends consisting of poly(4-butyltriphenylamine)(PBTPA),poly(methyl methacrylate)(PMMA)and PBTPA-block-PMMA were fabricated by a solvent evaporation method.Effects of the molecular weight and the chemical composition of PBTPA-b-PMMA,molecular weights of homopolymers,and the composition of the blend on the morphology were investigated.The polymer blend particle consisting of PBTPA and PMMA homopolymers exhibited thermodynamically favored core-shell structure,in which more hydrophilic PMMA-shell surrounded PBTPA-core.The addition of 10 wt%of PBTPA-b-PMMA caused the morphological transition from core-shell toJanus or inversed core-shell,in which PBTPA-shell surrounded PMMA-core,depending on the molecular weight of PBTPA segment in PBTPA-b-PMMA.When the molecular weight of PMMA segment was higher than that of PMMA homopolymer,watermelon-like particles in which small PBTPA domain less than 80 nm dispersed in the PMMA domain surrounded by PBTPA shell were observed.As the ratio of PBTPA-b-PMMA increased,the interface of the macrophase separation became obscure.At 50 wt%of the PBTPA-b-PMMA,only microphase separation was observed.The measurement of interfacial tension by pendant drop method demonstrated that PBTPA-b-PMMA lower the interfacial tension between PBTPA and the aqueous phase to the value similar to that of PMMA with the aqueous phase.
文摘Considering the inhomogeneity of the concentration distribution in the corona of a star\|shaped micelle, an equation system of free energy components was suggested in order to predict the micro\|phase separation of the diblock copolymer in selective solvents. All energetic and entropic contributions to the free energy of micellization were included in equations for the micellar solution, which was composed of the di\|block copolymers with certain molecular weights and the solvent with special characters at a giving temperature. The minimization of free energy produced the equilibrium size and aggregation number of the micelle. The corona and core size of the micelle,the concentration profile of the soluble block in corona and the value of the aggregation number were obtained based on the present theory. Moreover, the theoretical predictions of the aggregation number were in good agreement with the experimental data for systems of polystyrene\|poly(2\|cinnamoylethyl methacrylate)/cyclopentane and poly(4\|vinylpyridine) \|polystyrene/toluene.
文摘采用原子转移自由基聚合方法(A tom transfer rad ica l po lym erization,ATRP),以α-溴丙酸乙酯为引发剂,溴化亚铜和联二吡啶为催化体系,合成了端基为卤原子的单分散聚甲基丙烯酸甲酯(PMM A-X)预聚体。以此PMM A-X为大分子引发剂,在同样催化体系下,引发苯乙烯聚合,得到了分子量分布较窄的聚甲基丙烯酸甲酯-b-聚苯乙烯(PMM A-b-PS t)嵌段共聚物,并用红外光谱(IR)、核磁共振谱(1H-NM R)、凝胶渗透色谱(GPC)和透射电子显微镜(TEM)对其结构和形态进行了初步表征。结果表明,嵌段共聚物中聚甲基丙烯酸甲酯的质量百分数为28%,数均分子量(M n)为4.76×104,多分散系数(PD I)为1.49。经TEM表征,发现该嵌段聚合物具有周期性层状相分离结构,层状取向周期达到了400 nm左右,在紫外-可见波长范围内。这一特征长周期为嵌段共聚物材料用作光波导等光学器件提供了结构基础。
