Novel polymer synthetic pathways enable topologically complex architectures and hinge upon the continued improvement of functionalization strategies, including the facile fabrication of telechelic polymers. In ring-opening metathesis polymerization (ROMP), chain-end functionalized polymers have been achieved through a variety of techniques, including sacrificial synthesis, tandem ring-opening/ring-closing ene-yne ROMP, pulsed monomer addition, and chain-transfer agent (CTA) addition. While these existing methods are versatile and promising, none to our knowledge have been implemented in systems with complex architectures. Herein, we describe the preparation of homotelechelic bottlebrush polymers via grafting-through ROMP with various functional CTAs and macromonomers. In general, the degree of polymerization was found to be independent of catalyst concentration and dependent on the ratio of CTA to macromonomer. A library of polystyrene, poly(methyl methacrylate), and polyisobutylene-based bottlebrushes were generated with useful CTAs, including end-functionalized atom-transfer radical polymerization (ATRP) initiators, reversible addition-fragmentation chain-transfer (RAFT) CTAs, and UV-active chromophores. Bisfunctional bottlebrush macroinitiators were subsequently chain-extended with either activators regenerated by electron transfer (ARGET) ATRP or RAFT polymerization to afford novel ABA triblock copolymers. Importantly, this technique is a powerful, modular platform in which unique brush architectures and functionalization can be accessed in a few steps without arduous post-polymerization modification, thereby opening the way for increasingly versatile polymer topologies.

Versatile homotelechellic bottlebrush polymers via chain-transfer ring-opening metathesis polymerization

ACS Spring Meeting 2021

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