MOLECULAR DYNAMICS AND HETEROGENEITY OF THE STYRENE-ACRYLONITRILE COPOLYMERS AS VIEWED BY ELECTRON SPIN RESONANCE
Mladen Andreis, Zorica Veksli, Marko Rogošiæ and Helena Jasna
Ruðer Boškoviæ Institute, Bijenièka c. 54, HR-10000 Zagreb, Croatia
Faculty of Chemical Engineering and Technology, University of Zagreb, Maruliæev Trg 19, HR-10000 Zagreb, Croatia
Molecular mobility and heterogeneity of statistical and alternating copolymers of styrene and acrylonitrile have been studied in the wide temperature range by the ESR spin probe method using two nitroxyl radicals, Tempo and Tempone. The temperature at which the maxima separation becomes 5 mT decreases with increasing styrene content. At higher temperatures above the glass transition temperature the copolymers with the smaller amount of styrene reflect motional heterogeneity. The motional difference between the statistical and alternating copolymers of a similar composition are reconciled on the basis of the sequence structure of copolymer chains. The packing of segments and the formation of motionally different domains can be explored by the adequately chosen probe even if the homopolymers have very similar glass transition temperature but differ in the polar and packing features.