Molecular aggregation behavior of polyvinyl chloride solutions

In this work, the effects of the polymer-solvent interaction on the aggregation behavior of polyvinyl chloride (PVC) solutions were studied through elastic 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 temperature. 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 BrBz must be more extended than those in a poor solvent, DOA. The theta-temperatures are about 32 degrees C and 68 degrees C for PVC/BrBz and PVC/DOA solutions, respectively. The result in the temperature dependence of R-g value 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 heterogeneous than PVC/BrBz solution. The time-resolved light scattering measurements indicated that the spinodal decomposition rate of PVC/DOA solution was faster than that of PVC/BrBz solution. However, the gelation time of PVC/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 to 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 scattered maximum was observed in PVC/DOA solution while no other peak appeared in PVC/BrBz solution. The various aggregation or the gelation behaviors between 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 Science Ltd. All nights reserved.