Diastereoisomeric diversity dictates reactivity of epoxy groups in limonene dioxide polymerization

Abstract

Limonene dioxide (LDO) has the potential to find a wide application as a bio-based epoxy resin. Its polymerizations by catalyzed ring-opening, and by polyaddition with diamines were compared with the polymerizations of the commercial epoxy resins bisphenol-A diglycidyl ether (BADGE), and 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ECC). Differential scanning calorimetry (DSC) studies showed that LDO polymerizations suffer in all cases studied from incomplete conversions. Nuclear magnetic resonance (NMR) studies revealed that in cis-isomers of LDO the internal epoxide rings were not reacting. The low reactivity of this epoxide group was explained by mechanistic considerations making use of the Fürst-Plattner rule, or trans-diaxial effect. Due to diastereomeric diversity approximately one-fourth of epoxide groups present in LDO could not react. Therefore, a diastereoselective epoxidation of limonene could provide a fully reactive bio-based epoxy resin.

Keywords

• Biopolymers, biocomposites
• Thermosetting resin
• Thermal properties