Cardanol-based oligomers with “hard core, flexible shell” structures: from synthesis to UV curing applications
Two hyperbranched oligomers with renewable cardanol side groups and multiple photopolymerizable acrylates were designed and synthesized. The structures of the hyperbranched oligomers were characterized by 1H NMR and FTIR spectroscopy. The synthesized oligomers contain rigid carbon rings as “hard cores” and long reactive fatty chains as “flexible shells”. The photopolymerization kinetics, thermodynamic properties and mechanical properties of the UV cured films were studied and compared with a petrochemical based hyperbranched acrylate CN2302. The cardanol-based polymers with “hard core, flexible shell” structures have higher double bond conversion and higher Tg but lower thermal stability. Much improved surface mechanical properties such as nanoindentation hardness, reduced modulus, surface storage modulus and storage stiffness can be obtained for the plant oil-based polymers. These biorenewable, UV curable cardanol-based oligomers show promise in “green + green” materials technologies.