Solventless synthesis and free-radical photopolymerization of a castor oil-based acrylate oligomer

A simple, low environmental impact procedure for preparing acrylated castor oil (ACO) was developed using a hybrid acrylate isocyanate monomer. The photopolymerization of neat ACO and the co-polymerization of ACO with common low molecular weight acrylate monomers were rapid and reached high conversions, as monitored by real-time FT-IR spectroscopy. The mechanical properties of the ACO polymers and copolymers were determined by dynamic mechanical analysis of the thin polymer films. The resulting copolymers ranged from highly flexible, low glass transition materials to rigid, high glass transition materials depending on the functionality and secondary functional groups of the commercial monomers used. The ACO oligomer was compatible with a variety of acrylate monomers and produced transparent films regardless of co-monomer used. The glass transition temperatures of the copolymers can be coarsely estimated a priori using the Fox correlation. ACO-based materials provide a promising route to introduce renewable materials in many acrylate-based coating applications.