Synthesis of Syndiotactic Macrocyclic Poly(methyl methacrylate) via Transformation of the Growing Terminal in Stereospecific Anionic Polymerization

Abstract

In this study, the synthesis of well-defined cyclic syndiotactic poly(methyl methacrylate) (st-PMMA) is investigated by transformation of the growing terminal in stereospecific anionic polymerization. st-PMMA is first synthesized by living syndiospecific anionic polymerization in tetrahydrofuran at a low temperature, which is started with a protected-alkyne initiator prepared in situ by metal-halogen exchange reaction of an α-haloester bearing a pendent protected-alkyne with 1,1-diphenylhexyl lithium. The anionic polymerization is terminated with halogenation of the growing enolate terminal by CBrCl3. The terminal halogen of the obtained st-PMMA is further converted into azide group, which is subsequently employed in the intramolecular copper-catalyzed click reaction in high dilution with the alkyne-initiating terminal after deprotection. The macrocyclic st-PMMA is confirmed by 1H NMR, size exclusion chromatography, and MALDI-TOF MS analyses. (Figure presented.).