A Bicyclo[4.2.0]octene-Derived Monomer Provides Completely Linear Alternating Copolymers via Alternating Ring-Opening Metathesis Polymerization (AROMP)

Abstract

Strained bicyclic carbomethoxy olefins were utilized as substrates in alternating ring-opening metathesis polymerization and found to provide low-dispersity polymers with novel backbones. The polymerization of methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate with cyclohexene in the presence of the fast-initiating Grubbs catalyst (H ₂IMes)(3-Br-Pyr) ₂Cl ₂Ru=CHPh leads to a completely linear as well as alternating copolymer, as demonstrated by NMR spectroscopy, isotopic labeling, and gel permeation chromatography. In contrast, intramolecular chain-transfer reactions were observed with [5.2.0] and [3.2.0] bicyclic carbomethoxy olefins, although to a lesser extent than with the previously reported monocyclic cyclobutenecarboxylic ester monomers [ A. Song; K. A. Parker; N. S. SampsonJ. Am. Chem. Soc.2009, 131, 3444[ PubMed]]. Inclusion of cyclohexyl rings fused to the copolymer backbone minimizes intramolecular chain-transfer reactions and provides a framework for creating alternating functionality in a one-step polymerization.