Synthesis and photoinitiated cationic polymerization of epoxidized phenylpropanoid and α-pinene derivatives

Abstract

Phenylpropanoides and myrtenol were converted into laurates in a first reaction step followed by epoxidation of the olefinic structure using m-chloroperbenzoic acid to synthesize new epoxy monomers. These are epoxy eugenyl laurate (EEL), epoxy isoeugenyl laurate (EiEL), epoxy cinnamyl laurate (ECL), and epoxy myrtenyl laurate (EML). Cationic photoinitiated polymerization of the new epoxy monomers melting below or slightly above room temperature results in oligomers with a degree of polymerization between 2 and 6. The low degree of polymerization causes a glass transition temperature of the new oligoethers below the polymerization temperature indicating the neglecting influence of vitrification on the photoinitiated polymerization of these epoxy monomers. Significant differences were found regarding the kinetics of the cationic photoinitiated polymerization between the single new epoxy monomers and epoxy anethol (EA) as well as epoxy estragol (EE). The molar polymerization enthalpy determined for epoxy monomers undergoing quantitative conversion differs from the value for ethylene oxide that is known from the literature. This indicates the influence of the substituents bound at the epoxy group on the polymerization kinetics.