DYNAMIC LIGHT-SCATTERING-STUDIES OF POLY(4-CHLOROSTYRENE) AND POLY(2-CHLOROSTYRENE) IN THETA-SOLVENT

Most studies of coil-to-globule transitions of macromolecules have dea lt exclusively with the standard polystyrene-cyclohexane system. In th is work we aim to extend such investigations to halogenated polystyren es, namely poly(4-chlorostyrene)(PPCS), poly(2-chlorostyrene)(POCS) an d poly(chlorostyrene)(PCS),a mixture of 2- and 4-isomers. Changes in R -h Of these polymers with temperature in their respective theta solven ts were investigated by dynamic light scattering. The hydrodynamic siz e of PPCS in a-propyl benzene(M-W: 2.25 x 10(6) g mol(-1), M-W/M-n 1.1 6) decreases to 75% of that in the unperturbed state at 22.2 degrees C . POCS (M-W: 10.32 x 10(6) and M-W: 4.30 X 10(6), M-W/M-n: 1.10) in 2- butanone exhibited LCST behaviour and a Limited chain collapse was obs erved with increasing temperature above theta point. The parameters al pha(h) = R-h/R-h(theta) for POCS with two different molecular weights, (10.32 M and 4.30 M) were found to be 0.67 and 0.77, respectively at 37.0 degrees C. A smooth and continuous contraction was also observed for the mixture of 2- and 4-isomers, PCS (M-W: 2.32 x 10(6) g mol(-1), M-W/M-n: 1.06). (C) 1998 Elsevier Science Ltd. All rights reserved.