LARGE-SCALE HETEROGENEITIES IN ENTANGLED POLYMER-SOLUTIONS - LIGHT-SCATTERING STUDY ON POLYSTYRENE IN TOLUENE

Static and dynamic low-angle light-scattering experiments carried out on semidilute and moderately concentrated solutions of polystyrene in toluene provide evidence for the existence of heterogeneities in the e ntanglement network with correlation lengths of several hundred nanome ters. The slow mode showing up in the correlograms in addition to the gel mode reflects the diffusive motion of these chain associations. Th e tendency to form associations increases with the solute concentratio n and with decreasing temperature. The observations indicate that the reptation time does not represent the longest relaxation time in the s ystem; a complete reorganization of the entanglement network requires a much longer period.