DYNAMIC BEHAVIOR OF HIGH-MOLECULAR-WEIGHT POLYSTYRENE IN THE MARGINAL SOLVENT 2-BUTANONE

This article reports the dynamic properties of polystyrene in the marginal solvent 2-butanone at both dilute and semidilute concentrations. The first internal mode (tau-1), evaluated by use of dynamic light scattering in the range 0.75 < qR(g) < 1.4, is concentration-independent up to almost-equal-to C*/2, with a value agreeing with that predicted by the Zimm nondraining model. Above almost-equal-to C*/2, tau-1 decreases monotonically. Semidilute solutions in this system are characterized by the presence of a broad distribution of slow (possibly q-independent) modes in addition to the q2-dependent gel mode. The concentration dependence of the latter is characterized by xi approximately C-0.43 in agreement with earlier investigations. Renormalization group theory incorporating hydrodynamic screening provides a good description of the dynamic behavior in this marginal solvent system.