Preparation of spiro-shaped multicyclic polymer by combination of ATRP, CuAAC and photo-induced coupling

This paper elaborated the preparation of spiro-shaped multicyclic polymer with repeating heterocyclics. Block copolymer PEO-PS-Br was prepared by atom transfer radical polymerization (ATRP) of styrene (St) with a poly(ethylene oxide) telechelic macroinitiator PEO-Cou-Br, in which both ends of PEO chain were capped by coumarin groups in advance. After azidation of terminal bromine, bimolecular cyclization was conducted with a diyne as difunctional linker to provide heterocyclic polymer with coumarin groups at the boundaries between PEO and PS blocks. The heterocyclic polymer was exposed to UV irradiation at 365 nm to afford spiro-shaped multicyclic polymer via dimerization of coumarin. GPC, 1H NMR and FT-IR were used to characterize obtained products. Photocleavage of multicyclic polymer under irradiation of 254 nm was also investigated, and GPC trace suggests the successful cleavage from spiro-shaped structure to monocycles.