Visible Light Induced Controlled Cationic Polymerization Of Vinyl Ethers And Mechanism Investigation

The application of green polymerization method is the main development direction of preparing polymer materials in the future.Cationic polymerization is an important branch of polymer chemistry.It has irreplaceable advantages that its products such as butyl rubber play an important role in the automotive industry,medical equipment,aerospace research,and other fields.Traditional cationic polymerization must be carried out in anhydrous,oxygen-free,and ultra-low temperature(-100℃)environments.The operating conditions are harsh,with high operating costs and large energy consumption.Visible light-induced cationic polymerization is simple to operate,environmentally friendly,and low cost.It has become a research hotspot.In this thesis,based on visible lightinduced vinyl ether cationic polymerization,the living/controlled polymerization and copolymerization are studied.The specific research content is as follows:On the basis of the synthetic chain transfer agent S-1-isobutoxylethylS’-ethyl trithiocarbonate(CTA),the visible-light-induced cationic polymerization of isobutyl vinyl ether catalyzed by pyran salt(2,4,6-tris(pmethoxyphenyl)tetrafluoroborate was successfully achieved.The living polymerization characteristics were investigated.It was found that the molecular weight of polyisobutyl vinyl ether(PIBVE)increased with the increase of monomer conversion.The polymerization showed first-order reaction kinetics.The active center has the ability to sustainable polymerization.It enables to achieve block copolymerization of Poly(IBVE-b-IBVE).Combined with UV-vis absorption spectroscopy,fluorescence spectroscopy,and molecular orbital simulation,the relevant mechanism of polymerization reaction was proposed.The random copolymerization of propylene glycol ether(PVE),2-chloroethyl vinyl ether(CEVE),cyclohexyl vinyl ether(CyVE),and isobutyl vinyl ether(IBVE)were achieved by using a pyran salt-catalyzed photopolymerization system,respectively.The conditions of the copolymerization reaction were investigated.The influence of catalyst concentration,visible wavelength and other factors on the polymerization was explored.The reactivity ratios of IBVE with PVE,CyVE,and CEVE in copolymerization were calculated using the Yezreielv-Brokhina-Roskin method.It enables the adjustment of copolymerization composition.A photocontrolled cationic polymerization catalytic system was constructed using iridium complex catalyst(4,4-bis(trifluoromethyl)-2,2-bipyridine bis[3,5-difluoro-2-(5-trifluoromethyl-2-pyridyl)phenyl]iridium(Ⅲ)hexafluorophosphate)and chain transfer agent(1-isobutoxyethyl)ethyl trithiocarbonate,achieving the living/controlled polymerization of IBVE,PVE,CyVE,and n-butyl vinyl ether(BVE).By switching the "on" or "off" of the light source,it was demonstrated that the iridium complex photopolymerization system can achieve time control of polymerization,i.e.real-time control of "start" or "stop" of polymerization.Electrochemical analysis and simulation calculations were used to analyze and explain the light-controlled experimental phenomena of iridium complexes and pyran salt systems.This catalytic system not only enables the end-functionalization of polyisobutylene-based ethers through alcohol and acid substitution reactions but also produces random copolymers of IBVE with PVE,CyVE,BVE,and CEVE.