Radical polymerisation and thiol–ene post-polymerisation functionalisation of terpenoid acrylates in conventional and renewably sourced organic solvents

Abstract

Geranyl acrylate has been synthesized and polymerized by various radical polymerisation techniques. Due to the structural diversity, a number of post polymerisation functionalization options were explored. Monomer conversion, polymer structure and the molecular weight were assessed by NMR, FT-IR and size exclusion chromatography (SEC). Free radical polymerization and Cu-mediated reversible deactivation radical polymerization (RDRP) were used to synthesise poly(geranyl acrylate) of various molecular weight in both conventional petro-derived organic and bio-based renewably sourced solvents. Cu⁰ wire-mediated RDRP was found to be a suitable polymerisation method when compared to Cu^II-mediated photoinduced RDRP giving the optimal living radical polymerisation method for the synthesis of poly(geranyl acrylate) in Cyrene (M_n, SEC = 3000, Đ_SEC = 1.25). The residual allylic double bonds provided a useful option for post-polymerization modification. Poly(geranyl acrylate) was subjected to photoinduced thiol–ene reactions, using different thiols with a variety of functional groups. The success of the functionalization reaction was evaluated by NMR, FT-IR spectroscopy, and SEC. In addition, differential scanning calorimetry was used to investigate changes in the thermal properties of the polymer, before and after thiol–ene functionalization.