Iterative Preparation Of Hyperbranched Polymer By Selective Addition Of Asymmetric Polythiol And Asymmetric Diene

Hyperbranched polymers have a highly branched molecular structure,relatively accurate molecular weight and extremely narrow molecular weight distribution.Its intramolecular segments are not easily entangled,giving them low viscosity characteristics.Meanwhile,a large number of terminal functional groups can be carried around the molecular periphery,which makes them have a wide application prospect in many fields such as composite materials,coatings,imaging,biomedicine,nano carriers and so on.In this article,hyperbranched poly(ester-thioether)will be prepared by using the efficient click chemical reaction of asymmetric polythiol and asymmetric diene monomers which differences in functional group activity.The specific research contents are as follows:A novel asymmetric polythiol thioglycolic acid(4-oxo-1,7-dimercapto)-2-heptyl ester is synthesized by ring opening and addition reaction of allyl glycidyl ether and thioacetic acid,followed by transesterification with methanol,and finally esterification with thioglycolic acid;the other thiol is prepared by esterification of 2-mercaptoethanol and thioglycolic acid.The asymmetric diene monomer glycerin-1,2-dimethacrylate-3-acrylate is prepared by ring opening reaction of glycidyl methacrylate and acrylic acid,and then esterification with methacryloyl chloride;the other diene is prepared by esterification of hydroxyethyl methacrylate and acrylic acid.These asymmetric monomers are characterized by ~1H NMR and FT-IR.Based on the differences in nucleophilic addition reactivity of different thiol groups of asymmetric thiols and double bond of methacrylate and acrylate in asymmetric diene,taking TMPTA and Di-TMPTA as the core,thiol-ene click addition with asymmetric polythiol is performed first,and then the reaction with asymmetric diene monomer.With the repeated iteration of the reaction,the first to the third generation hyperbranched poly(ester-thioether)is prepared.Due to the obvious difference of solubility between the polymer and the monomer involved in the reaction in ether,the polymer and the excess monomer can be separated by simple sedimentation.Through the ~1H NMR,FT-IR and GPC,the nucleophilic addition iteration process tracking found that the thiol and double bonds appeared alternately,the polymer molecular weight gradually increased with the generation,and the polymer molecular weight distribution was narrow(M_w/M_n=1.03-1.23),the polydispersity index increases slightly with the increase of algebra.This study enriches the synthesis of hyperbranched poly(ester-thioether).