Living Polymerization Of Vinyl Pyridine Catalyzed By Novel Phosphine-based Frustrated Lewis Pairs

Lewis Pair Polymerization（LPP）,as a new polymerization method,has received widespread attention in polymer synthesis since its advent in 2010.In recent years,LPP systems have been used to achieve the living control polymerization of various polar vinyl monomers and lactones,as well as the sequential control polymerization of various methacrylate monomers.Due to the special structures of 2-vinylpyridine（2VP）and 4-vinylpyridine（4VP）,their polymers or polymers containing vinylpyridine are widely used in self-assembly,nanoelectronic devices,supramolecular polymers,ion exchange resin materials,biological materials,drug delivery,and other fields.2VP and4VP are conjugated structures（C=C-C=N/C=C-C=C-C=N/N）formed by the direct connection of vinyl and pyridine at positions 2 or 4.They can be used for anionic polymerization,free radical polymerization,coordination insertion polymerization,and LPP.Currently,the reported polymerization methods for 2VP mainly include free radical polymerization and coordination insertion polymerization;The polymerization methods of 4VP mainly include anionic polymerization and free radical polymerization.However,using the above polymerization systems generally has the problems of low initiation efficiency and large catalyst consumption.Therefore,this article has developed a Lewis Pairs（LPs）catalyst based on a new organic super strong phosphine base to solve the above problems.In the second chapter,we synthesized new monoguanidine substituted organic super phosphine bases（NI^tBu）PPh₂ and new biguanidine substituted organic super phosphine bases（NIⁱPr）₂PPh and（NI^tBu）₂PPh.By regulating the steric hindrance of Lewis acid（LA）and Lewis base（LB）and their respective electrophilicity and nucleophilicity,we developed LPs systems based on（NIⁱPr）₂PPh/Al Ph₃·OEt₂ and（NI^tBu）₂PPh/Al Ph₃·OEt₂,and used them to achieve the living control polymerization of 2VP and 4VP,respectively,Poly（2-vinylpyridine）（P2VP）with a number average molecular weight of M_n up to 219 kg/mol and poly（4-vinylpyridine）with M_n=287kg/mol were obtained.We have experimentally demonstrated that the（NI^tBu）₂PPh/Al Ph₃·OEt₂LPs system is a living control polymerization system for 4VP,including a linear increase in polymer molecular weight with increasing monomer ratio（R²=0.9897）and maintaining a narrow molecular weight distribution（1.15-1.37）,with an initiation efficiency maintained between 90%and 105%;Two chain extension experiments were successfully carried out on 4VP,and a well-defined diblock polymer（P4VP-b-PDMAA）was synthesized.For the LPs system composed of（NIⁱPr）₂PPh and Al Ph₃·OEt₂,the active controllable polymerization of 2VP can be achieved.As the monomer weight of 2VP increases,the molecular weight of P2VP increases linearly（R²=0.9909）,and the molecular weight distribution remains within a narrow range（1.27-1.54）.Two chain extension experiments have been successfully conducted on2VP.In Chapter 3,based on the composite sequence control strategy of LPP for monomer mixtures,using the differences in the coordination ability of ethoxyethyl methacrylate（EEMA）and 2VP with Al Ph₃·OEt₂,we can adjust the monomer race ratio by controlling the feed amount of Al Ph₃·OEt₂,thereby realizing the regulation of the sequence structure of the copolymer.When the amount of LA is less than 36 equivalents（relative to LB）and the ratio of the two monomers is equal,the two monomers undergo gradient copolymerization to varying degrees to generate polymer PEEMA-b-（PEEMA-r-P2VP）-b-P2VP.When the amount of LA was 36 equivalents,block polymerization of EEMA and 2VP was successfully achieved,and amphiphilic block copolymer PEEMA-b-P2VP was synthesized.The GPC test curve shows that the above polymers have a single peak distribution,with a molecular weight of between 54 kg/mol and 89 kg/mol.The initiation efficiency of the catalytic system remains between 58.7%and 96.1%depending on the amount of LA used.We have proved that the obtained polymer is a block polymer with well-defined structure through nuclear magnetic resonance DOSY two-dimensional spectroscopy,and DSC analysis.