Bio-derived polymers for coating applications: comparing poly(limonene carbonate) and poly (cyclohexadiene carbonate)

Two fully bio-based polycarbonates, poly(cyclohexadiene carbonate) (PCHDC) and poly(limonene carbonate) (PLC), are synthesised from carbon dioxide and cyclohexadiene oxide and limonene oxide. The low molecular weight polycarbonates are cross-linked by a photoinitiated reaction with trimethylolpropane tris(3-mercaptopropionate), via thiol-ene reactions. The cross-linking reactions are monitored using Raman spectroscopy and the reaction temperatures and times are optimised. Kinetic analyses of the cross-linking process suggest diffusion-controlled reactions for both polymers, despite the differences in the nature of alkene moieties (terminal vs. internal alkene). The resulting materials are evaluated for coating applications, they show promising solvent resistance and hardness and may be used in the future to prepare scratch-resistant coatings.