Effect Of Polysaccharide Derivatives On Free Radical Polymerization Behavior Of Methyl Methacrylate

Most vinyl monomers are polymerized by free radical polymerization,which is the most widely used chemical reaction in the polymer synthesis industry.But due to the uncontrollability of the reaction process,most of polymers are random.In actual production,fundamental properties of polymers are sensitively linked to their tacticity.At present,there are many reports on the use of ionic polymerization or coordination polymerization to achieve the stereocontrol,but few related studies on the behavior and stereocontrol of free radical polymerization.In addition,due to the poor symmetry of the molecular structure and high degree of polarization of the methyl methacrylate monomer,the propagating group has high reactivity and low stability,which can lead to uncontrollable chain transfer and side reactions.Therefore,controlling the stereochemical configuration of polymers is a huge challenge in polymer synthetic chemistry and there are few reports on improving the isotacticity of polymers.Based on this situation,this topic proposes to use polysaccharide derivatives with regular helical structures as chiral additives to study the influence of the polymerization method and polymerization behavior of methyl methacrylate,and further explore the effect of polysaccharide derivatives on the stereoregularity of polymethyl methacrylate.Firstly,cellulose-tris(3,5-dimethylphenylcarbamate)(CDMPC)and amylose-tris(3,5-dimethylphenylcarbamate)(ADMPC)were synthesized by a urethanization reaction with 3,5-dimethylphenyl isocyanate as derivatization reagent,and the structure was characterized by FT-IR and ~1H NMR spectroscopy.Then,polymethyl methacrylate were synthesized by free radical polymerization with polysaccharide derivatives as chiral additives.Furthermore,the influence of the ratio of additives,the infiltration state,reaction solvent and other conditions on the tacticity of polymethyl methacrylates obtained from free radical polymerization were discussed.The results show that the use of chiral polysaccharide derivatives as chiral additives can significantly improve the isotacticity of the polymethyl methacrylate(PMMA)obtained in free radical polymerization.With the increase of the ratio of polysaccharide derivatives,the stereoregularity of the obtained PMMA is also higher.In addition,the polymers obtained by using amylose derivatives as chiral additives have higher stereoregularity,which may be due to the weaker backbone rigidity of amylose derivatives,which makes it easier to adjust the stacking arrangement of molecular chains and side groups and improve the chance of contact with monomer or active chain.PMMA obtained by using non-polar solvents has a more obvious effect on the stereoregularity of the polymer than polar solvents.This may be due to the fact that the polar solvent will greatly weaken the interaction between the monomer and the chiral polysaccharide derivative,thereby weakening the influence of the chiral polysaccharide derivative on the polymerization behavior of methyl methacrylate during the free radical polymerization.The maximum isotacticity of PMMA obtained with n-octane as the reaction solvent and CDMPC as the chiral additive is 0.45,and the maximum isotacticity of PMMA with ADMPC as the chiral additive is 0.74,which is the highest value currently reported.