A novel synthesis of PP-b-PMMA copolymers via metallocene catalysis and borane chemistry

Abstract

This paper describes a novel route to prepare polypropylene diblock copolymers, such as PP-b-PMMA, which comprise a polypropylene and free radical polymerized polymer segment. The chemistry involves a transformation process from metallocene catalysis to borane chemistry. Firstly, polypropylene with chain end unsaturation was prepared by metallocene catalysts, such as Et(Ind) 2ZrCl 2/MAO. Secondly, the olefinic chain end was hydroborated by 9-BBN to produce borane terminated PP. Thirdly, the borane group at the chain end was selectively oxidized and interconverted to polymeric radical which then initiated radical polymerization to produce diblock copolymers. Despite the heterogeneous reaction conditions, the overall yield and structure of diblock copolymers are quite satisfactory. In addition, the chain extension process, showing no significant broading in molecular weight distribution, implies a ‘stable’ radical polymerization.