Aliphatic urethane model compounds

Aromatic urethane model compounds (Urethanes I and II) were studied in the crystalline form to identify the characteristic Amide bands in the interface region when freed of any interactions with urea or polyether segments. Aliphatic urethane model compounds (Urethanes III and IV) were studied to identify the influence of aromatic rings on particular bands. The 1800-1200 cm-1 regions of aromatic Urethane I and aliphatic Urethane III are shown in Figure 3. 

In a preliminary study also involving model compounds [81], the kinetics of urethane formation was followed by FTIR spectroscopy using an aliphatic and an aromatic monoisocyanate and their homologous diisocyanates. Both the model reactions and the polymer synthesis gave clear cut second-order behaviour, indicating that the hydroxyl groups borne by the suberin monomers displayed conventional aliphatic-OH reactivity. 

Carothers et al. separated and characterized a variety of oligomers by fractional crystallization of aliphatic polyesters of adipic acid. In 1939, the dimeric and trimeric cyclic compounds of e-caprolactam were separated, and linear oligomers from monomer to pentamer (oligomers of nylon-6) were prepared. The linear oligomers were used as model substances for viscosimetric studies. The cyclic urethane oligomers formed from hexamethylene diisocynate with diols were reported in 1941, and systematic investigation on the cyclic and linear oligomers of nylon-6 were performed in the early 1950 s. 

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