A new approach to synthesize liquid crystalline polymer with narrow polydispersity index（PDI） was developed.Photopolymerization of 4-cyanophenyl-4＇-（6-acryloyloxyhexyloxy）benzoate（RM23） in nematic liquid crysta...A new approach to synthesize liquid crystalline polymer with narrow polydispersity index（PDI） was developed.Photopolymerization of 4-cyanophenyl-4＇-（6-acryloyloxyhexyloxy）benzoate（RM23） in nematic liquid crystals with macroscopic orientation was studied.The effects of the monomer concentration on the molecular weight and PDI of the resulting polymers were studied through gel permeation chromatography（GPC） and polarized optical microscopy.The low PDI of 1.19 and 1.22 was obtained in the reverse and normal modes,respectively.The PDI and molecular weight increased with monomer concentration.展开更多
Photo-polymerization is at the foundation of many industries such as dentistry,coatings,adhesives,and stereolithography 3D printing.However,the organic cationic photo-initiators currently used are toxic,expensive,and ...Photo-polymerization is at the foundation of many industries such as dentistry,coatings,adhesives,and stereolithography 3D printing.However,the organic cationic photo-initiators currently used are toxic,expensive,and difficult to tune with respect to the wavelength of light required to initiate polymerization reactions.For example,current stereolithography 3D printing resins are unstable under sunlight.Here,we demonstrate that less expensive and non-toxic titania quantum dots made via the scalable flame spray pyrolysis technology can photo-polymerize epoxy when exposed to UVC(not present in sunlight on Earth),while being insensitive to UVA(present in natural sunlight on Earth)leading to resins that are photo-stable during end use.We use NMR and FTIR to demonstrate that photo-polymerization is catalyzed under UVC but not UVA,and nanoindentation to monitor the mechanical stability of epoxy films during postpolymerization UVA exposure.This approach allows precise control over the wavelengths of light under which photo-polymerization can and cannot occur,and is also transferable to other photo-catalytic reactions.展开更多
In this paper,a fully bio-based vinyl oligomer with high functionalities was successfully prepared from rapeseed oil by three modification steps:epoxidation of rapeseed oil,solvent-free and catalyst-free ring opening ...In this paper,a fully bio-based vinyl oligomer with high functionalities was successfully prepared from rapeseed oil by three modification steps:epoxidation of rapeseed oil,solvent-free and catalyst-free ring opening by 10-undecylenic acid followed by esterification with 10-undecenoyl chloride.Then,the renewable polymers were prepared by photo-polymerization of these modified vegetable oils with typical thiol monomers:pentaerythritol tetrakis(3-mercaptopropionate),pentaerythritol tris(3-mercaptopropionate)and 1,2-ethanedithiol.The synthesis of the vinyl oligomer was monitored by nuclear magnetic resonance and Fourier-transform infrared spectroscopy.The average number of the carbon-carbon double bonds of the resulting vinyl oligomer is high to be 7.2.The kinetic of thiol-ene photo-polymerization of vegetable oil-based vinyl oligomer was studied by FTIR-ATR analyses.In addition,the thermo-physical properties,thermal stability and solvent resistance of these UV cured films were characterized.The polymers from 1,2-ethanedithiol exhibit higher gel content,storage modulus and glass transition temperature than those from other thiol monomers due to the high crosslinking densities of the resulting polymers.All polymers show excellent thermal stability up to 290oC.The resulting polymers exhibit thermo-physical properties,excellent water resistance and thermals stability,which is promising to find application in coatings and adhesives.展开更多
基金The authors are grateful to NSF of China(No.50703013)Independent Innovative Position of Hubei Province for financial support of this work
文摘A new approach to synthesize liquid crystalline polymer with narrow polydispersity index（PDI） was developed.Photopolymerization of 4-cyanophenyl-4＇-（6-acryloyloxyhexyloxy）benzoate（RM23） in nematic liquid crystals with macroscopic orientation was studied.The effects of the monomer concentration on the molecular weight and PDI of the resulting polymers were studied through gel permeation chromatography（GPC） and polarized optical microscopy.The low PDI of 1.19 and 1.22 was obtained in the reverse and normal modes,respectively.The PDI and molecular weight increased with monomer concentration.
文摘Photo-polymerization is at the foundation of many industries such as dentistry,coatings,adhesives,and stereolithography 3D printing.However,the organic cationic photo-initiators currently used are toxic,expensive,and difficult to tune with respect to the wavelength of light required to initiate polymerization reactions.For example,current stereolithography 3D printing resins are unstable under sunlight.Here,we demonstrate that less expensive and non-toxic titania quantum dots made via the scalable flame spray pyrolysis technology can photo-polymerize epoxy when exposed to UVC(not present in sunlight on Earth),while being insensitive to UVA(present in natural sunlight on Earth)leading to resins that are photo-stable during end use.We use NMR and FTIR to demonstrate that photo-polymerization is catalyzed under UVC but not UVA,and nanoindentation to monitor the mechanical stability of epoxy films during postpolymerization UVA exposure.This approach allows precise control over the wavelengths of light under which photo-polymerization can and cannot occur,and is also transferable to other photo-catalytic reactions.
基金sponsored by the National Natural Science Foundation of China(51563011)the Natural Science Foundation of Jiangxi Province(2016BAB203094)+1 种基金the Young Talents Project of Jiangxi Science and Technology Normal University(2016QNBJRC007)the Postgraduate Innovation Fund Project of Jiangxi Science and Technology Normal University(YC2019-X31).
文摘In this paper,a fully bio-based vinyl oligomer with high functionalities was successfully prepared from rapeseed oil by three modification steps:epoxidation of rapeseed oil,solvent-free and catalyst-free ring opening by 10-undecylenic acid followed by esterification with 10-undecenoyl chloride.Then,the renewable polymers were prepared by photo-polymerization of these modified vegetable oils with typical thiol monomers:pentaerythritol tetrakis(3-mercaptopropionate),pentaerythritol tris(3-mercaptopropionate)and 1,2-ethanedithiol.The synthesis of the vinyl oligomer was monitored by nuclear magnetic resonance and Fourier-transform infrared spectroscopy.The average number of the carbon-carbon double bonds of the resulting vinyl oligomer is high to be 7.2.The kinetic of thiol-ene photo-polymerization of vegetable oil-based vinyl oligomer was studied by FTIR-ATR analyses.In addition,the thermo-physical properties,thermal stability and solvent resistance of these UV cured films were characterized.The polymers from 1,2-ethanedithiol exhibit higher gel content,storage modulus and glass transition temperature than those from other thiol monomers due to the high crosslinking densities of the resulting polymers.All polymers show excellent thermal stability up to 290oC.The resulting polymers exhibit thermo-physical properties,excellent water resistance and thermals stability,which is promising to find application in coatings and adhesives.
