Amphiphilic star-block copolymers composed of polystyrene and poly（acrylic acid） were synthesized by iodide- mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN...Amphiphilic star-block copolymers composed of polystyrene and poly（acrylic acid） were synthesized by iodide- mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN as initiator and 1,1,1-trimethyolpropane tri（2-iodoisobutyrate） as chain transfer agent, giving iodine atom ended star-shaped polystyrene with three arm chains, R（polystyrene）3. Secondly, tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent, and star-block copolymer, R（polystyrene-b-poly（tert-butyl acrylate））3 with controlled molecular weight was obtained. Finally, amphiphilic star-block copolymer, R（polystyrene-b-poly（acrylic acid））3 was obtained by hydrolysis of R（polystyrene-b-poly（tert-butyl acrylate））3 under acidic condition.展开更多
1 Results Highly branched poly(methyl methacrylate) (PMMA) stars were prepared by one-pot approach based on N,N-diethyldithiocarbamate-(DC) mediated living radical photo-polymerization.Soluble alternating hyperbranche...1 Results Highly branched poly(methyl methacrylate) (PMMA) stars were prepared by one-pot approach based on N,N-diethyldithiocarbamate-(DC) mediated living radical photo-polymerization.Soluble alternating hyperbranched microgel formation was initiated fast with preferential consumption of inimer 4-vinylbenzyl N,N-diethyldithiocarbamate (VBDC) and 4,4′-bismaleimidediphenylmethane (BMIM) in the presence of an excess of methyl methacrylate (MMA),PMMA arms could then grow from DC groups of microgel as macro...展开更多
A dissipative particle dynamics simulation technique was used to investigate the effect of molecular architecture of star-block copolymer on the patterned structure in a nanodroplet. With increasing the ratio of solvo...A dissipative particle dynamics simulation technique was used to investigate the effect of molecular architecture of star-block copolymer on the patterned structure in a nanodroplet. With increasing the ratio of solvophilic to block length to solvophobic block length（RwT）, solvophobic sphere, ordered hexagonal phase, onion phase, perforated onion phase and flocculent phase are formed, respectively. Since onion phase has potential application in controlled drug release, it has received wide attention experimentally and theoretically. Our simulation indicates onion phase forms at a certain RH/T（close to but less than 1）. A star-block copolymer molecule has two conformations in onion phase： either fully located in a shell or shared by two neighboring shells. Central structure affects onion＇s final shape. The molecular number of the copolymer in each shell is a quadratic function of the shell＇s radius. The arm number of star-block copolymer has little influence on onion＇s structure, but slightly affects the solvent content. Additionally, we studied the influence of arm length on onion＇s structure.展开更多
Eight-arm star-shaped poly（■-caprolactone）-block-poly（ethylene glycol）s（SPCL-b-PEG） have been prepared by a combination of controlled ring-opening polymerization（CROP） and coupling reaction. First, eight-arm ...Eight-arm star-shaped poly（■-caprolactone）-block-poly（ethylene glycol）s（SPCL-b-PEG） have been prepared by a combination of controlled ring-opening polymerization（CROP） and coupling reaction. First, eight-arm star-shaped poly（■-caprolactone）s（SPCL） with a resorcinarene core were synthesized using octamethyl tetraundecylresorcinarene octaacetate as octa-initiator and yttrium tris（2,6-di-tert-butyl-4-methylphenolate） [Y（DBMP）3] as catalyst. Then the coupling reaction was carried out between SPCLs and carboxyl-terminated methoxy poly（ethylene glycol）s（mP EG-COOH） in the presence of N,N′-dicyclohexylcarbodiimide（DCC） and 4-dimethylaminopyridine（DMAP）, resulting in eight-arm star-shaped SPCL-b-PEGs with controlled molecular weight and well-defined architecture. Furthermore, these amphiphilic eight-arm SPCL-b-PEGs could self-assemble into micelles with low critical micellar concentrations（CMC）, which was characterized by fluorescent spectroscopy. Moreover, indomethacin loaded micelles with high drug loading content and high encapsulation efficiency can be prepared, which is probably due to the highly branched architecture. The morphologies of micelles were characterized by transmission electron microscopy（TEM）, which exhibited diverse nanostructures as the drug loading contents varied. In vitro drug release of indomethacin from SPCL-b-PEG micelles was carried out in PBS, from which a sustained release behavior was observed. SPCL-b-PEG micelles did not show significant cytotoxicity at copolymer concentrations up to 1000 mg/L, making them very promising for drug delivery.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
基金The authors gratefully acknowledge the support from Beijing Municipal Commission of Education.
文摘Amphiphilic star-block copolymers composed of polystyrene and poly（acrylic acid） were synthesized by iodide- mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN as initiator and 1,1,1-trimethyolpropane tri（2-iodoisobutyrate） as chain transfer agent, giving iodine atom ended star-shaped polystyrene with three arm chains, R（polystyrene）3. Secondly, tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent, and star-block copolymer, R（polystyrene-b-poly（tert-butyl acrylate））3 with controlled molecular weight was obtained. Finally, amphiphilic star-block copolymer, R（polystyrene-b-poly（acrylic acid））3 was obtained by hydrolysis of R（polystyrene-b-poly（tert-butyl acrylate））3 under acidic condition.
文摘1 Results Highly branched poly(methyl methacrylate) (PMMA) stars were prepared by one-pot approach based on N,N-diethyldithiocarbamate-(DC) mediated living radical photo-polymerization.Soluble alternating hyperbranched microgel formation was initiated fast with preferential consumption of inimer 4-vinylbenzyl N,N-diethyldithiocarbamate (VBDC) and 4,4′-bismaleimidediphenylmethane (BMIM) in the presence of an excess of methyl methacrylate (MMA),PMMA arms could then grow from DC groups of microgel as macro...
基金Supported by the National Natural Science Foundation of China（No.51209024）, the Science and Technology Plan of Sichuan Province, China（No.2010JY0122）, the Science Research Fund of Sichuan Normal University, China（No.10MSL02） and 251 Key Talent Program of Sichuan Normal University, China.
文摘A dissipative particle dynamics simulation technique was used to investigate the effect of molecular architecture of star-block copolymer on the patterned structure in a nanodroplet. With increasing the ratio of solvophilic to block length to solvophobic block length（RwT）, solvophobic sphere, ordered hexagonal phase, onion phase, perforated onion phase and flocculent phase are formed, respectively. Since onion phase has potential application in controlled drug release, it has received wide attention experimentally and theoretically. Our simulation indicates onion phase forms at a certain RH/T（close to but less than 1）. A star-block copolymer molecule has two conformations in onion phase： either fully located in a shell or shared by two neighboring shells. Central structure affects onion＇s final shape. The molecular number of the copolymer in each shell is a quadratic function of the shell＇s radius. The arm number of star-block copolymer has little influence on onion＇s structure, but slightly affects the solvent content. Additionally, we studied the influence of arm length on onion＇s structure.
基金supported by the National Natural Science Foundation of China(Nos.20704036 and 21274121)the Major State Basic Research Project(No.2011CB606001)
文摘Eight-arm star-shaped poly（■-caprolactone）-block-poly（ethylene glycol）s（SPCL-b-PEG） have been prepared by a combination of controlled ring-opening polymerization（CROP） and coupling reaction. First, eight-arm star-shaped poly（■-caprolactone）s（SPCL） with a resorcinarene core were synthesized using octamethyl tetraundecylresorcinarene octaacetate as octa-initiator and yttrium tris（2,6-di-tert-butyl-4-methylphenolate） [Y（DBMP）3] as catalyst. Then the coupling reaction was carried out between SPCLs and carboxyl-terminated methoxy poly（ethylene glycol）s（mP EG-COOH） in the presence of N,N′-dicyclohexylcarbodiimide（DCC） and 4-dimethylaminopyridine（DMAP）, resulting in eight-arm star-shaped SPCL-b-PEGs with controlled molecular weight and well-defined architecture. Furthermore, these amphiphilic eight-arm SPCL-b-PEGs could self-assemble into micelles with low critical micellar concentrations（CMC）, which was characterized by fluorescent spectroscopy. Moreover, indomethacin loaded micelles with high drug loading content and high encapsulation efficiency can be prepared, which is probably due to the highly branched architecture. The morphologies of micelles were characterized by transmission electron microscopy（TEM）, which exhibited diverse nanostructures as the drug loading contents varied. In vitro drug release of indomethacin from SPCL-b-PEG micelles was carried out in PBS, from which a sustained release behavior was observed. SPCL-b-PEG micelles did not show significant cytotoxicity at copolymer concentrations up to 1000 mg/L, making them very promising for drug delivery.
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.
