Effect of Spacer Unit on Photo-Initiated Thermal Crosslinking of Polymers Having Carbamoyloxyimino Groups in Side-Chains

Abstract

Carbamoyloxyimino (COI) groups are known to generate amino groups photochemically and isocyanato groups thermally, and these generated groups have been used for highly efficient crosslinking systems. In this article, a series of polymers which were connected to COI groups with or without spacer units were prepared, and their crosslinking behavior on irradiation followed by heating was investigated to clarify the effect of the length of side-chain. There was no effect of spacer units on photoreactivity of COI groups. On the other hand, thermal reactivity of COI groups in polymers with spacer unit was faster than that in polymers without spacer unit. Thermogravimetric analyses and real-time IR spectroscopy revealed lower thermal decomposition temperature, lower glass transition temperature, and higher thermal decomposition rate of COI groups in copolymers with spacer unit compared to corresponding polymers without spacer unit. These behaviors were reflected on the crosslinking on irradiation followed by heating, where films of polymers with spacer unit showed more effective insolubilization than those without spacer unit. Other factor such as comonomer and the presence of α-methyl group on main-chain were also investigated.