Molecular aggregation behavior of polyvinyl chloride solutions

In this work, the effects of the polymer-solvent interaction on the aggrega tion behavior of polyvinyl chloride (PVC) solutions were studied through el astic Light scattering and viscosity measurements. The result in Zimm plots of PVC solutions showed that the second viral coefficient, A(2), value of PVC/BrBz solutions is higher than that of PVC/DOA solutions at the same tem perature. The radius of gyration, R-g, in PVC/BrBz solutions is larger than that in PVC/DOA solutions, indicating that PVC chains in a good solvent Br Bz must be more extended than those in a poor solvent, DOA. The theta-tempe ratures are about 32 degrees C and 68 degrees C for PVC/BrBz and PVC/DOA so lutions, respectively. The result in the temperature dependence of R-g valu e showed that PVC/BrBz solution exhibits the coil-globule transition, while no transition is observed in PVC/DOA solution in the measured temperature range. The chain overlapping concept was used to discuss the heterogeneous degree of PVC solution. The result showed that PVC/DOA solution is more het erogeneous than PVC/BrBz solution. The time-resolved light scattering measu rements indicated that the spinodal decomposition rate of PVC/DOA solution was faster than that of PVC/BrBz solution. However, the gelation time of PV C/BrBz solution was shorter than that of PVC/DOA solution. These facts may imply that the more extended chains in PVC/BrBz solution are advantageous t o the intermolecular association for the gelation. The scattered profiles ( l(q) vs. q) showed that the scattered intensity of PVC/DOA solution is much higher than that of PVC/BrBz solution at the same concentration. A scatter ed maximum was observed in PVC/DOA solution while no other peak appeared in PVC/BrBz solution. The various aggregation or the gelation behaviors betwe en PVC/DOA and PVC/BrBz solutions must be concerned with different degrees of spinodal decomposition in the solution state, which is mainly related to different degrees of the polymer-solvent interaction. (C) 1999 Elsevier Sc ience Ltd. All nights reserved.