Polyamideurethans of structures I and II were prepared by reacting N,N′-di-(6-hydroxycaproyl)alkylenediamines and N-hydroxyalkyl-6-hydroxycaproamide with hexa-methylene diisocyanate and 4,4′-diphenylmethane diisocyanate:
where R1 is either a dimethylene or hexamethylene radical, and R2 is a hexamethylene or 4,4′-diphenylmethane radical. Polymers I and II were of a high degree of polymerization and crystallinity, had high enough melting points for practical use, and gave colorless tough films both by dry and melt castings. The polymers from hexamethylene diisocyanate were much more crystalline and thermally more stable above the melting points than those from 4,4′-diphenylmethane diisocyanate. Polymerization conditions and characteristic properties of the resulting polymers were studied.