Environmentally friendly polyurethanes based on non-isocyanate synthesis

A series of environmentally friendly non-isocyanate polyurethanes (NIPUs) was synthesized through a polycondensation reaction of as-synthesized semi-bio-based bis-cyclic carbonate with diamine derivatives. The synthesis of biscyclic carbonate was realized, for the first time, from 1-thioglycerol and polyethylene glycol diacrylate via thiol-ene click and transcarbonation reaction, respectively. The impacts of using different diamine derivatives on the chemical structural, mechanical properties, thermal stability, and surface wettability of the NIPUs were determined. It was found that the NIPU containing fatty acid-based diamine decomposed at a lower temperature than that of other polymers. Besides, it demonstrated a lower Young's modulus and a higher tensile strain at break, possibly due to its four-branched structure and greater flexibility. Meanwhile, the NIPU prepared with p-xylylenediamine provided the highest decomposition temperature, owing to an aromatic moiety in the polymer's backbone, which improved its stiffness and thermal stability. Furthermore, it was understood that the NIPU containing diamino-N-methyldipropyl-amine exhibited a higher Young's modulus and a lower tensile strain at break, as it had a nitrogen atom in its structure and a trigonal pyramidal configuration with the highest density of hydrogen bonds between polymer chains. Most of the developed NIPUs displayed hydrophobic surface properties, offering promising alternatives to isocyanate-based coating materials.