Polyurethanes

摘要

Cyclic oligomers having low melt viscosity compared to linear counterparts have been synthesised.Aryl carbodiimides are suitable for ring opening polymerisation and can be prepared direcdy from isocyanates.The N-acylurea duly formed by mixing the carbodiimide with carboxylic acids at room temperature can rearrange to an amide at higher temperatures in the range of 100-150°C.It is reported that the preparation proceeds via sequential self-repetitive reaction process to produce a macrocyclic ether-urethane carbodiimide,which is a key intermediate for poly(amide-urethane)s and poly(amide-imide-urethane)s.