Construction Of Heterogeneous Photocatalyst System For PET-RAFT Polymerization

The popularization of environment-friendly chemistry has promoted the development of polymer synthesis towards the green direction of high efficiency and innovation.One of the main challenges of polymerization chemistry is the use of green processes to develop new materials with precise structure and properties for use in multidisciplinary fields such as biomedical and composite materials.To address this challenge,the combination of photochemistry and reversible inactivated radical polymerization provides good reaction control and simplifies complex reaction processes.Among them,photoinduced electron/energy transfer-reversible additionbreak chain transfer polymerization(PET-RAFT)has become an innovative strategy to cope with the above challenges due to its versatility,spatiotemporal controllability and environmental benignity.However,for the application in the biomedical field,the residue of the catalyst,will bring on significant toxic effects to the synthesized products.Therefore,the design and development of biocompatible photocatalysts that are easy to separate and recover are the key factors to successful photopolymerization of biomedical products.Therefore,two biocompatible heterogeneous catalysts are designed for PET-RAFT polymerization research,and the attempt is made to expand the application prospects for highthroughput photopolymerization.Specific research contents mainly include:(1)Ultra-thin Zn-Zn PPF-2D nanosheets were synthesized by surfactant-assisted method,and PET-RAFT polymerization was carried out as a heterogeneous photocatalyst.Compared to three-dimensional metal-organic frameworks,the catalyst has extremely high catalytic efficiency,enabling a precise and efficient photopolymerization.Studies of polymerization of multiple monomers in low-volume plates shown that the ultra-thin nature of the catalyst has a larger specific surface area and a more accessible catalytic site for efficient capture of light energy.The amount of catalyst can be reduced to the range of 10～200 ppm,showing higher polymerization efficiency than Zn-Zn PPF-3D,and the monomer conversion reached 90% under 2 h yellow light radiation.In addition,triblock copolymers can be successfully synthesized with one-off feeding of catalysts without repeated deoxygenation and purification,and the monomer conversion was greater than 98%.Finally,the synthesis of polymers in human cell culture media showed the potential application of this catalytic system in the biomedical field.(2)NCPNIEY catalyst was prepared by coupling eosin Y,which linked a temperature-sensitive copolymer,to the surface of chitin nanofiber microspheres by active ester-amine reaction,and it was used for PET-RAFT polymerization.The results show that the heterogeneous catalyst has strong spatiotemporal control ability for polymerization.AMP polymerization was performed in 96-well plates,and the monomer conversion exceeded 90% after 6 h of light illumination,while maintaining the dispersity coefficient less than 1.2.The NCPNEY microsphere catalyst was recycled for 6 times and the thriblock copolymer was successfully synthesized.In addition,the synthesis of polymer-protein bioconjugates was achieved in multi-well plates.The catalytic system used the temperature sensitivity of surface copolymer brushes to separate and recover NCPNEY microspheres by controlling the temperature of the reaction mixture,and the purification of protein-polymer bioconjugates was readily completed without affecting protein activity.