Preparation Of Hyperbranched Poly (Thioether-ester) Via Thiol-ene Click And Esterification Iterative

Dendritic/hyperbranched polymers are widely used in many fields such as self-assembly, drug carrier, coating and so on, and the synthetic method of these polymers have risen to the force. The dendrimers synthesized by divergent and convergence methods have a lot of disadvantages, such as complicated synthetic steps and difficult purification, but also hyperbranched polymers prepared via one-pot synthesis have many structural defects. Recently, click chemistry on how to synthesize dendritic/hyperbranched polymers with greatly effective and convenient methods gain more and more attention. In this paper, we prepared dendritic/hyperbranched poly(thioether-ester) through the iteration of thiol-ene click reaction and esterification.We prepared glycerol mono allyl ether and pentaerythritol single allyl propyl ether using common industrial raw materials like glycerine, pentaerythritol,mercaptopropionic acid, etc. through the simple protection, etherification and de-protection. Pentaerythritol four mercapto propionic acid ester as a nucleus in the subsequent click chemistry was prepared by direct esterification. 1H NMR and GC-MS revealed that synthesized monomer and the nuclear are consistent with target products and the purity is higher.We obtained the first generation of hyperbranched poly(thioether-ester) with terminated thiol through the direct esterification between the first generation of hyperbranched poly(thioether-ester) with terminated hydroxyl and Mercaptopropionic acid using the method of azeotropic dehydration, then repeating the above reaction, and finally we prepared hyperbranched poly(thioether-ester) with higher generation. The conditions of click reaction in this paper were mild, rapid and high efficient and fewer by-products.Esterification is simple and easy to manage. We utilize the difference dissolution between hyperbranched poly(thioether-ester) and excess monomers and choosing the right solvent to precipitate with higher yield of the hyperbranched poly(thioether-ester).1H NMR, GPC, MALDI-TOF-MS revealed that we have obtained hyperbranched poly(thioether-ester) within three generations with cleat structure, narrow molecular weight distribution, fewer defects.Research showed the molecular weight distribution of polymers with terminated hydroxyl have no obvious increasing after click reaction, but the molecular weight distribution of polymers increased obviously after esterification,especially the esterification using 3-mercaptopropionic acid other than 2-mercapto propionic acid, it indicated ester exchange have happened during the esterification of polymers with terminated hydroxyl.All the research showed iteration of thiol-ene click reaction and esterification with highly efficiency and conbenience is an effective way for the preparation of the hyperbranched poly(thioether-ester) with narrow molecular weight distribution and fewer defects.