Synthesis and Ozone Degradation of Alternating Copolymers of N-Substituted Maleimides with Diene Monomers

Radical copolymerization of N-substituted maleimides (RMIs) and maleic anhydride (MAn) in combination with 2,4-dimethyl-1,3-pentadiene (DMPD) and 1,3-pentadiene (PD) provides alternating copolymers with excellent thermal stability. Onset temperatures of decomposition are 280-331 and 336-371 degrees C for the copolymers with DMPD and PD, respectively. Glass transition temperatures of RMI copolymers are in a wide range of 54-138 degrees C depending on the bulkiness of N-substituents. MAn copolymers are transformed to the corresponding RMI copolymers by postpolymerization reactions, which consist of quantitative addition of an alkylamine to an anhydride moiety of MAn copolymers and the subsequent heating. The copolymers synthesized in this study include ozone-degradable carbon-to-carbon double bonds in their main chain. Molecular weight of the copolymers rapidly decreases by ozone degradation. Surface modification of casted polymer films is also performed by exposure to ozone-containing air.