Reactivities of, N-Alkylcitraconimides in the Radical Copolymerizations with Styrene or Methyl Methacrylate

Abstract

The radical copolymerizations of N-alkylcitraconimide (RCI: R=C2H5, n-C3H7, i-C3H7, n-C4H9, i-C4H9, t-C4H9, n-C6H13, C6H5CH2) (M1) with styrene (ST) (M2) or methyl methacrylate (MMA) (M2) were carried out at 60°C, using azobisisobutyronitrile as the initiator in tetrahydrofuran in order to clarify the substituent effect on the copolymerizations. From the results obtained, the monomer reactivity ratios and the Q1 and e1 values were determined. It was found that the relative reactivities (1/r2) of RCI toward attack of a polystyryl radical could be correlated only by the polar-substituent constant (σ*) of the alkyl group in RCI, not by the steric-substituent constant (Es) in Taft’s equation: log (1/r2)=ρ*σ*+δEs. According to the above equation, the ρ* and δ values were obtained as 0.34 and 0, respectively, in the RCI–ST system. On the other hand, in the RCI–MMA system, both the ρ* and δ values were 0; that is, neither the polar nor the steric character of alkyl group in RCI contributed to the relative reactivities (1/r2) of the RCI toward attack of a poly(MMA) radical. It was also observed that both the Q1 and e1 values for RCI were independent of Taft’s σ* -substituent constant.