Synthesis of block and graft copolymers of β-pinene and styrene by transformation of living cationic polymerization to atom transfer radical polymerization

Abstract

The transformations of living cationic polymerization to ATRP to form the block and graft copolymers of β-pinene with styrene were performed. Poly(β-pinene) carrying benzyl chloride terminal [poly(β-p)StCl] was prepared by capping the living poly(β-pinene), which was obtained with 1-phenylethyl chloride/TiCl 4/Ti(O iPr) 4/ nBu 4NCl initiating system, with a few units of styrene. Poly(β-p)StCl, in conjunction with CuCl and bpy, could initiate the ATRP of styrene and gave well-defined block copolymer of β-pinene and styrene. In contrast, tert-alkyl-chlorine-capped poly(β-pinene) [poly(β-p)Cl] obtained by living cationic polymerization of β-pinene per se without capping of styrene gave a mixture of desired block copolymers and unreacted poly(β-p)Cl due to the low initiating reactivity of poly(β-p)Cl. Brominated poly(β-pinene) synthesized by the quantitative bromination of poly(β-pinene) using NBS was also used to initiate the ATRP of styrene in the presence of CuBr and bpy to prepare the graft copolymer of β-pinene and styrene. The first-order kinetic characteristic and linear increment of molecule weight with the increasing of monomer conversion indicated the living nature of this ATRP grafting.