Preparation of star polymers based on polystyrene or poly(styrene- b- N-isopropyl acrylamide) and divinylbenzene via reversible addition-fragmentation chain transfer polymerization

Abstract

Star polymers based on styrene/divinyl benzene (St/DVB) and PSt- b-poly( N-isopropyl acrylamide) (NIPAAM)/DVB have been successively prepared by ‘arm-first’ method via reversible addition-fragmentation chain transfer (RAFT) polymerization. The linear macro RAFT agent PSt-SC(S)Ph was prepared by RAFT polymerization of St using benzyl dithiobenzoate and AIBN as RAFT agent and initiator. Successive RAFT polymerization of NIPAAM with PSt-SC(S)Ph as macro RAFT agent to afford diblock copolymer, PSt-b-PNIPAAM-SC(S)Ph. The coupling reactions of PSt-SC(S)Ph or PSt-b-PNIPAAM-SC(S)Ph in the presence of DVB produced the star copolymers, C(PSt) n or C(PSt-b-PNIPAAM) n . The molar ratio of DVB/PSt-SC(S)Ph and polymerization time influenced the yields, molecular weight and distribution of the star-shaped polymers, which was characterized by 1H NMR and IR spectra, GPC measurements as well as DLS.