SEQUENCE CHANGE OF POLY(N-ACYLURETHANE)S BASED ON TRANSESTERIFICATION

Modification of poly(N-acylurethane)s (3 a-c) by transesterification w ith hexyl alcohol and 2-dodecyl-1,3-propanediol (2 a) under mild condi tions was studied. 3 were prepared by polyaddition of corresponding bi s(N-acylisocyanate)s and diols under mild conditions in good yields. R eaction of poly(N-acylurethane) (3 a) ((M) over bar(n) = 22700) with t wo equivalents of hexyl alcohol started around 100 degrees C to give t he corresponding degradation products ((M) over bar(n) = 7300, 120 deg rees C, 90 min). A mixture of poly(N-acylurethane) (3 b, (M) over bar( n) = 17500) with an equimolar amount of 2a was heated at 150 degrees C under reduced pressure to remove 1,2-propanediol. The polymer obtaine d was 3a of which yield and (M) over bar(n) were 57% and 6900, respect ively. Transesterification of N-acylurethane derived from phenol proce eded easier than that derived from alkanol. Aromatic poly(N-acyluretha ne (3c) derived from 4,4'-dihydroxydiphenyl ether (2c) underwent a sim ilar transesterification with 2a at lower temperature (80 degrees C) w ithout removal of 2c to give 3a in 43% yield. Thus, the modification o f poly(N-acylurethane)s (3) could be readily achieved by the transeste rification with mono alcohols and diols under mild conditions without any catalyst.