Synthesis and characterization of alternating diblock copolymer via RAFT polymerization

Abstract

We demonstrated a novel synthetic method for the preparation of alternating diblock copolymer[(ST-alt-MA)-b-(MA-alt-IPA)] by using various monomer pairs that undergo alternating copolymerization. The diblock copolymer is composed of two distinct alternating copolymer chains. The polymerization was carried out with three monomers, maleic anhydride (MA), styrene (ST) and isopropenyl acetate (IPA), via reversible addition-fragmentation chain transfer (RAFT) polymerization. Formation of diblock copolymer was driven by the reactivity differences between the comonomer pairs (ST:MA, MA:IPA). More reactive comonomer pair, MA and ST, was polymerized first to form alternating copolymer chains one block, and then subsequent copolymerization of the remaing pair, MA and IPA, produced alternating diblock copolymers. Block chain length was controlled easily by stoichiometric control of monomer pairs. The structure and composition of the diblock alternating copolymer were characterized by 1H NMR , 13C NMR and FT-IR spectroscopy. Gel permeation chromatography (GPC) analysis showed that the diblock copolymers had controlled molecular weight and narrow molecular weight distribution around 1.2. Thermal properties of the diblock copolymers were investigated by TGA and DSC.