Efficient Synthesis and PISA Behavior of Molecular Bottlebrush Block Copolymers via a Grafting-From Strategy through RAFT Dispersion Polymerization

Abstract

Precise synthesis of molecular bottlebrushes (MBBs) with high yield via the grafting-from strategy using a reversible deactivation radical polymerization (RDRP) technique has remained elusive. Herein, the molecular bottlebrush block copolymers (MBB BCPs) with high yield and varying chemical compositions were synthesized via a polymerization-induced self-assembly (PISA)-assisted grafting-from strategy by reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization. First, the poly(norbornene-g-poly(ethylene oxide))-b-poly(norbornene-g-chain transfer agent) [P(NB-g-PEG45)-b-P(NB-CTA)] BCPs with varied chemical compositions were synthesized by sequential ring-opening metathesis polymerization (ROMP) of norbornene PEG macromonomers (NB-PEG45) and norbornene chain transfer agent (NB-CTA) monomers. Subsequently, these P(NB-g-PEG45)m-b-P(NB-CTA)n BCPs were used as multifunctional macro-CTAs for the synthesis of MBB BCPs with a high yield (up to 80% styrene monomer conversion) and a low dispersity (Đ < 1.15) via a grafting-from strategy through RAFT dispersion polymerization. The PISA behaviors of these MBB BCPs were also investigated, and the results indicated that the MBB BCPs assemblies were transformed from spherical micelles into two-dimensional disk-like micelles because the rigidity of the PS MBB segment increased with the growth of PS side chains.