High performance thiol-ene thermosets based on fully bio-based poly(limonene carbonate)s

High glass transition temperature (Tg) thiol-ene networks (TENs) based on poly(limonene carbonate)s (PLCs), derived from orange oils and of potential degradability are described here. PLCs with moderate molecular weight were prepared by copolymerization of limonene oxide with CO2 and subsequent breakdown reactions. These PLCs were cured with multifunctional thiol monomers in the presence of thermal initiators via thiol-ene chemistry to generate poly(thioether-co-carbonate) networks. The thermal curing experiments were optimized by a kinetic study using real-time ATR-FTIR, in which a delayed gelation was observed. For the first time, an interesting “cage” effect was observed during the network formation initiated by DCP, in which the addition reactions of pendant isopropenyls on high molecular weight PLC chains were significantly enhanced by thiol-ene crosslinking at 160 °C. The resulting homogeneous TENs with high Tgs (>100 °C) and a wide range of thermomechanical properties, including rubbery moduli from 2.9 to 28.2 MPa, were obtained. The TENs also showed promising properties such as high transparency, good acetone resistance and high hardness, suggesting their potential application in coatings.