Isocyanate-free fabrication of sustainable polyurethane/POSS hybrid materials with tunable thermo-mechanical response

This work reports on the synthesis of non-isocyanate polyurethanes (NIPUs) obtained via the polyaddition of diamines: dimer fatty acid-derived diamine (DFA diamine) or polyether diamine (PPO diamine) with five-membered tri(cyclic carbonate) by a pre-polymerization method. The obtained NIPUs were further chemically modified by polyhedral oligomeric silsesquioxane (POSS) - glycidylisobutyl POSS (1epPOSS). The resulting reinforced composites, containing 5, 10 or 15 wt% 1epPOSS, were characterized in terms of their structure (FTIR, NMR, XRD), microstructure (SEM-EDS) and thermo-mechanical properties (DMA). FTIR confirmed the formation of polyurethanes, and NMR proved the chemical incorporation of 1epPOSS. XRD and SEM-EDS showed a uniform distribution of 1epPOSS in the matrix for low 1epPOSS concentration, with some agglomeration effects depending on the concentration of 1epPOSS. DMA indicated mechanical reinforcement of NIPUs based on DFA diamine. For NIPUs synthesized with PPO diamine, the composite with the highest 1epPOSS loading (15 wt%) exhibited superior mechanical properties in comparison to the pristine matrix, confirmed by both DMA and static stretching test.