Block Copolymers by the Conversion of Living Lithium Initiated Anionic Polymerization into Living Ruthenium ROMP

Abstract

This paper describes a method for the synthesis of well-defined AB block copolymers, where one block is synthesized via anionic polymerization initiated with alkyllithium compounds, and one by ring opening metathesis polymerization (ROMP) using well-defined ruthenium macroinitiators. This methodology was demonstrated by copolymerizing styrene with norbornene derivatives. Polystyrene was synthesized via living anionic polymerization initiated by sec-butyllithium, and functionalized to form macromonomers. These were used as precursors to well-defined ruthenium macroinitiators, the macromonomers being converted by an alkylidene exchange reaction with ruthenium propylidene initiator RuCl2(CHEt)(PCy3)2. These macroinitiators were used to initiate the ROMP of various norbornene derivatives in order to synthesize well-defined block copolymers with narrow molecular weight distributions.