Syntheses and crosslinking reactions of self‐curable copolymers containing pendant cyclic iminoethers and carboxylic acid groups

Abstract

AbstractSoluble copolymers containing both pendant cyclic iminoethers such as 4,4‐dimethyl‐2‐oxazoline or 4,4,6‐trimethyl‐4H‐dihydro‐1,3‐oxazine and carboxylic acid were successfully synthesized by radical copolymerizations of 4,4‐dimethyl‐2‐vinyl‐2‐oxazoline, 4,4‐dimethyl‐2‐isopropenyl‐2‐oxazoline, or 4,4,6‐trimethyl‐2‐vinyl‐4H‐dihydro‐1,3‐oxazine with methacrylic acid and styrene, methyl methacrylate, or ethyl acrylate using AIBN as an initiator in benzene or DMF at 60 or 80°C. The crosslinking reaction of the copolymers obtained did not occur by heating at 70°C. However, these copolymers quantitatively produced gel products by heating at 130°C. The rate of crosslinking reaction of the copolymer increased with increasing pendant cyclic iminoether and carboxylic acid groups. The rate of crosslinking was also affected by the molecular motion of the polymer chain.Our results show that the copolymers of more sterically hindered 2‐vinyl‐2‐oxazolines are more stable and so they can be crosslinked in a controlled manner and at higher temperatures than the previously studied polyoxaziline system.