EFFECT OF ALKYL SUBSTITUENTS ON THE RADICAL COPOLYMERIZATION OF N-ALKYLISOMALEIMIDES

Radical copolymerizations of N-alkylisomaleimides (RIMI: RQ = C2H5, CH2C6H5, CH2CH2C6H5, t-C4H9) (M2) with methyl methacrylate (MMA) (M1) were carried out at 70-degrees-C by using 2,2'-azobisisobutyronitrile as the initiator in 1,4-dioxane in order to clarify the substituent effect of RIMI. From the results obtained, the monomer reactivity ratios and Q2 and e2 values were determined. The relative reactivities (1/r1) of RIMI containing n-butyl and phenyl substituents previously reported for the attack of a poly(MMA) radical were correlated with the polar substituent constant (sigma*) for the substituent of RIMI in the Taft's equation, log(1/r1) = rho*sigma* + delta-E(s). The rho* and delta were estimated to be 0.5 and 0, respectively. The Q2 and e2 values for RIMI were also correlated with Taft's constants, and increased with increasing sigma* value of substituents. The introduction of electron-accepting substituent into RIMI led to a more conjugated structure of isomaleimide. The results were also compared with those of the n-alkylmaleimides.