Special structures and thermal stabilities of polyurethanes derived from diol and triol having oxazolidone moieties

We synthesized regular polyurethanes from the diol having oxazolidone structure (Diol-1) and the aliphatic diisocyanate by typical polyaddition. The results of the structural analysis suggested that the polyurethane having a cyclic urethane structure such as oxazolidone formed a rod-like structure, although the control polyurethane having a chain urethane structure formed a linear structure. The polyaddition of Diol-1 and aliphatic diisocyanate with triol having oxazolidone structure (Triol-1) as a crosslinker also proceeded successfully to achieve corresponding polyurethanes. However, the polyurethanes containing a molar ratio of Triol-1 less than or equal 50% were soluble in high polar organic solvents nevertheless those polyurethanes contained some trifunctional units in the polymer chain. On the other hand, the polyurethanes containing a molar ratio of Triol-1 more than 50% were insoluble in any organic solvents. We hypothesized that the soluble polyurethanes containing Triol-1 formed multi-branched structure and the insoluble polyurethanes formed cross-linking structure. Such structures of polymer chain affected significantly to the thermal properties of the obtained polyurethanes.