Sequence change of poly(N‐acylurethane)s based on transesterification

Abstract

AbstractModification of poly(N‐acylurethane)s (3a–c) by transesterification with hexyl alcohol and 2‐dodecyl‐1,3‐propanediol (2a) under mild conditions was studied. 3 were prepared by polyaddition of corresponding bis(N‐acylisocyanate)s and diols under mild conditions in good yields. Reaction of poly(N‐acylurethane) (3a) (Mn = 22700) with two equivalents of hexyl alcohol started around 100°C to give the corresponding degradation products (Mn = 7 300, 120°C, 90 min). A mixture of poly(N‐acylurethane) (3b, Mn = 17500) with an equimolar amount of 2a was heated at 150°C under reduced pressure to remove 1,2‐propanediol. The polymer obtained was 3a of which yield and Mn were 57% and 6900, respectively. Transesterification of N‐acylurethane derived from phenol proceeded easier than that derived from alkanol. Aromatic poly(N‐acylurethane) (3c) derived from 4,4′‐dihydroxydiphenyl ether (2c) underwent a similar transesterification with 2a at lower temperature (80°C) without removal of 2c to give 3a in 43% yield. Thus, the modification of poly(N‐acylurethane)s (3) could be readily achieved by the transesterification with mono alcohols and diols under mild conditions without any catalyst.