Precise Synthesis Of CO₂-Responsive Polymers And Their Applications In Smart Catalysis Systems

Metal nanoparticles catalysts have extremely high catalytic activity,unfortunately their application is largely hindered by the difficulties in improving their stability and their recyclability.CO2-responsive material can significantly change its physical and chemical properties when the external atmosphere changes,thus providing an efficient way to achieve rapid product separation and green catalysts recovery.However,the existing CO2-responsive materials still face problems such as poor recyclability,inability to regulate reaction progress and catalytic activity,and limited applicability to aqueous reaction systems.We designed and precisely synthesized a series of CO2-responsive polymers to meet the requirements of homogeneous and emulsion catalytic systems for controllable reaction and efficient catalyst recycling.Additionally,the effect of polymer structure on reaction progress and recovery efficiency was also investigated.The CO2-responsive polymers are further applied in controllable hydrogen generation.The research contents of this dissertation include:(1)the synthesis of CO2-responsive star copolymer and the core-shell nanoreactors that were subsequently produced by in-situ reduction method.The dispersibility,CO2-responsiveness,and stability of metal nanoparticles were studied.We further investigated the catalytic performance of the nanoreactors by choosing the reduction of 4-nitrophenol as a case study.(2)The preparation of CO2-responsive microgels loaded with metal nanoparticles to investigate the effects of structural parameters on its CO2-responsiveness and its ability to stabilize Pickering emulsion.A dynamic Pickering emulsion was synthesized to catalyze the silane oxidation and olefin hydrogenation to explore the mechanism of"saturation phenomenon".The catalytic activity,applicability,and recovery ability of microgels-supported metal nanoparticles were studied.(3)The preparation of CO2-responsive microgels and in-situ cross-linking at the interfaces of Pickering emulsion to study the effect of cross-linking on emulsion stability and CO2-responsiveness.The thermo and pH dual-responsive emulsion was prepared to study the controllable hydrogen generation.The main conclusions of this work can be summarized into the following points:(1)The unimolecular nanoreactors based on core-shell star copolymers were prepared through "chain-walking" polymerization of ethylene,followed by atom transfer radical polymerization and in-situ reduction method.The nanoreactors can effectively control the catalytic activity and reaction process.It also allows easy recycling for subsequent usage.The catalytic activity of the nanoreactor was comparable to that of homogeneous catalysts,while it maintains the rapid recyclability often associated with heterogeneous catalysts,thus providing novel applications for CO2-responsive materials.(2)The CO2-responsive microgels were prepared by soap-free emulsion polymerization to stabilized Pickering emulsion and support metal nanoparticles.A dynamic emulsion catalysis system was constructed to avoid the "saturation phenomenon" at Pickering emulsion interfaces,thus realizing high catalytic activity and efficient recovery of the catalysts,CO2-responsive polymers were extended to build smart catalysis system for organic phase.(3)CO2-responsive microgels were cross-linked in-situ at the oil-water interface to avoid the "saturation phenomenon" and the double emulsion for controllable hydrogen generation was further constructed by introducing phase change material.The mass transfer of substrates was regulated by temperature and pH,achieving controllable generation of hydrogen.This material is expected to be highly applicable in the energy field.