Novel Approaches To The Synthesis of Clicked Block Copolymers

Abstract

Block copolymers are widely used in both the academic and industrial communities due to their unique properties. With the development of living polymerization techniques, the synthesis of block copolymers with controlled molecular weights and unique architectures has reached an all time high. Here a novel approach to the synthesis of block copolymers, namely polystyrene-b-polyisoprene, using azide-alkyne click chemistry techniques is investigated. Both azido and alkyne-terminated polystyrene were synthesized using ATRP. Azido-terminated polystyrene was synthesized via a substitution reaction between NaN3 and bromo-terminated polystyrene. Alkyne-functionalized polystyrene was synthesized using propargyl 2-bromoisobutyrate as a functional initiator. ¹H NMR and SEC were used to analyze the degree of polymer functionalization. Anionic polymerization techniques were used to synthesize polyisoprene. Polyisoprenyl lithium was reacted with propylene oxide to obtain hydroxyl-terminated polyisoprene. Functionalization of ≥ 90% was demonstrated via flash column chromatography. The aforementioned hydroxyl-terminated polyisoprene was reacted with both 11-chloroundecanoyl bromide and 11-chloroundecanoyl chloride to synthesize halogen-terminated polyisoprene. As with polystyrene, a substitution reaction with NaN3 afforded azido-terminated polyisoprene. Alkyne-functionalized polystyrene was coupled with azido-terminated polyisoprene via click chemistry to create said block copolymers. The reactions were investigated using ¹H and ¹³C NMR, SEC, IR and in some cases TEM. The clicked block copolymers should provide precedent for the synthesis of supramolecular block copolymers.