Solvent- and catalyst-free synthesis of fully biobased nonisocyanate polyurethanes with different macromolecular architectures
A bis(cyclic carbonate) based on a dimeric fatty acid was successfully synthesized. The chemical structure of the original cyclic carbonate and its intermediates were determined by FTIR and NMR analyses. The cyclic carbonate reacted with a dimer-based diamine to give a fully biobased nonisocyanate polyurethane (NIPU), without a solvent and catalyst. Different macromolecular architectures were obtained. The influence of the cyclic carbonate:amine ratio, and the effect of the average amine functionality were investigated by chemical, thermal and rheological analyses, respectively. These parameters strongly impact the final NIPU properties. Comparison with NIPUs based on linear structures show the effect of the architecture introduced by the dimer-based building blocks on the resulting NIPU properties. To evaluate the real potential of these novel materials, NIPUs were also compared to conventional polyurethanes with equivalent architectures.