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

Since the concept of Frustrated Lewis Pairs（FLP）has been reported by Stephan and Erker.FLP has been developing rapidly in the field of small molecules,and has made remarkable achievements.Compared with the well-established application of FLPs in the small molecule chemistry,Lewis pair polymerization（LPP）exhibits promising prospect in the field of macromolecular synthesis,especially in the polymerization of polar vinyl monomers.However,the existing LPP catalyzed polar vinyl monomer polymerization systems generally have the disadvantages of wide molecular weight distribution,low initiation efficiency and chain termination side reactions.Therefore,the development of new LPP living polymerization system for polar vinyl monomer is of great significance to the development of LPP.Here,we have developed a novel phosphine-based Frustrated Lewis Pairs living polymerization polar vinyl monomers system.In Chapter Ⅱ,Herein five sterically hindered P（NIⁱPr）R₂ with the same imidazolin framework but varied substituents on the N atom were synthesized and employed to combine with a series of organoaluminum LAs to achieve an immortal FLP catalyst system for living polymerization of MMA at RT,producing PMMA with medium to ultrahigh molecular weight（UHMW）（up to 1927 kg/mol）,narrow MWD and high to quantitative initiation efficiencies.The P（NIⁱPr）Ph₂/（BHT）AlⁱBu₂ FLP living polymerization system has been unequivocally verified by several lines of evidence,including predicted polymer number-average molecular weight coupled with low dispersity values,high to quantitative initiation efficiencies,a linear increase of polymer M_n vs.monomer conversion and monomer-to-initiator ratio,high monomer-to-initiator ratio multiple chain extensions and well-defined diblock and triblock copolymers.Systematic investigation revealed that the combination of extraordinarily effective polymerization activity,exclusive zwitterionic active species and immortal polymerization process without observance of side reaction or chain termination enabled P（NIⁱPr）Ph₂/（BHT）AlⁱBu₂ FLP system to accurately control over polymerization of MMA and achieve UHMW PMMA in the end.These findings provide significantly important foundation to synthesis of UHMW polymer in the future.In Chapter Ⅲ,this contribution represents the living and controlled polymerization of naturally renewable cyclic acrylic monomers,such as MBL（α-methylene-γ-butyrolactone）and itsγ-methyl derivative MMBL（γ-methyl-α-methylene-γ-butyrolactone）catalyzed by a noninteracting frustrated Lewis pair system composed of a strong organophosphorus superbase P（NIⁱPr）Ph₂ and sterically encumbered but modestly strong organoaluminum Lewis acid（4-Me-2,6-^tBu₂-C₆H₂O）₂AlⁱBu（（BHT）₂AlⁱBu）.The livingness of MMBL polymerization has been unequivocally verified by evidences including predictable polymer molecular weight（M_n up to 195 kg/mol）and narrow molecular weight distribution（MWD as low as 1.02）,a linear increase of polymer M_n vs.monomer conversion and monomer-to-initiator ratio,well-defined chain extension experiments,and synthesis of diblock,triblock,and random copolymers.The systematic investigation towards the synergistic effects between strong nucleophilic P（NIⁱPr）R₂ and organoaluminum with different Lewis acidity and steric hindrence enabled us to achieve the first example of living/controlled（co）polymerization of MBL and MMBL by P（NIⁱPr）R₂-based FLP at RT,thus further expanding the utility of FLP chemistry.In Chapter Ⅳ,we used P（NIⁱPr）Ph₂/（BHT）AlⁱBu₂ FLP living polymerization system for the first time to synthesize sequence-controlled polymers.In this paper,we have been selected MMA,EMA,MEMA,EEMA four kinds of monomers as sequence monomers,with different hydrophilicity and hydrophobicity,to synthesize high molecular weight,multi-block and multi-monomer sequence-controlled polymers.The sequence-controlled polymers with high blocks（as high as 53 segments）,high molecular weight（up to 310kg/mol）and narrow molecular weight distribution（as low as 1.15）.To the best of our knowledge,this is for the first time sequence-controlled polymers with high molecular weight and high blocks was achieved in polymer synthesis under mild conditions so far.This work has further expanded the application of LPP.