Transformation of copolymerization mechanism of N-phenyl maleimide and ethyl phenylacrylate in the mixture of dioxane and pyridine

The copolymerization of N-phenylmaleimid (NPMI) with ethyl phenylacrylate ( EPA) in a mixture of dioxane (DIO) and pyridine (Py) was investigated. The apparent monomer reactivity ratio r(1) (NPMI) = 0.07 +/- 0.01 and r(2) (EPA ) = 0.09 +/- 0.02 in DIO was turned to r(1) (NPMI) = 3.67 +/- 0.07 and r(2) (EPA) = 0 +/- 0.03 in Py. The copolymerization of NPMI and EPA with the fi xed feed ratio (mol/mol 1 : 1) in different volume ratio of DIO/Py showed t hat the copolymer composition might be varied in a wide range from the 93.5 % of NPMI contents in copolymer to 48.7%. When the volume fraction of Py in the mixture of DIO and Py was <10%, the copolymer with nice alternating st ructure was obtained and the copolymerization could be inhibited completely by hydroquinone; if the fraction of Py was >10%, the following two kinds o f copolymers were formed: a copolymer in which the content of NPMI increase d with the Py and the copolymerization also could be inhibited by hydroquin one and a copolymer with low molecular weight almost completely composed of homopolymer of NPMI and is not affected by radical inhibitor as hydroquino ne. The transformation of the copolymerization mechanism from the radical t o anionic, which was dependent on the volume ratio of DIO and Py, was sugge sted. (C) 1999 John Wiley & Sons, Inc.