Synthesis of Brush Copolymers Based on a Poly(1,4-butadiene) Backbone via the “Grafting From” Approach by ROMP and ATRP

Abstract

The synthesis of brush copolymers based on a strictly 1,4-polybutadiene (PB) backbone is reported via the “grafting from” strategy by combining two highly controlled polymerization methods: ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). ROMP of a cis-3,4-disubstituted cyclobutene derivative (inimer) containing two initiating sites for ATRP was first investigated with Grubb’s first-generation catalyst ((Cy3P)2RuCl2(CHPh)), leading to well-controlled polymerization for DPn up to 75. The well-defined 1,4-polybutadiene backbones obtained (Mn,SEC ranging from 3600 to 25 200 g·mol−1, PDI ≤ 1.16) were then used as macroinitiators in ATRP with styrene, methyl methacrylate, and tert-butyl acrylate. While styrene polymerization led to nonnegligible side reactions, well-defined PB-g-poly(methyl methacrylate) (Mn,SEC = 19 900−98 200 g mol−1, PDI ≤ 1.20) and PB-g-poly(tert-butyl acrylate) (Mn,SEC = 36 600−140 000 g mol−1, PDI ≤ 1.21) were obtained through this synthetic approach. In addition, the morphology of a PB-g-poly(tert-butyl acrylate) was studied through AFM measurements.