Light scattering studies on aggregation behavior of polyvinyl chloride/dioxane solutions

In this work, the aggregation behavior of polyvinyl chloride/dioxane (PVC/DOA) solution was discussed through light scattering and viscometric measurements. From the static light scattering results, PVC/DOA solution has a negative value of the second virial coefficient, A2 value (ca. 23:65 £ 10 24 cm 3 mol g 22 U at 308C, implying that a repulsive force appeared between PVC chains and DOA. The dynamic light scattering results indicate that the dynamic behavior of PVC solution could be classified into three regions by increasing the concentration of PVC. In the infinite dilution region,âhaC , 1; the single relaxation mode is considered related to the translational diffusion of the individual PVC coil. In the hydrodynamic screen region, 1 ,âhaC , 4; the relaxation time distribution was divided into two major relaxation modes; i.e. the fast mode resembled that of the individual PVC coil in the dilute solution, and the slow mode is considered related to the cluster formed from the aggregation of several individual coils. At higher concentrations, âhaC . 4; the polymer coils start to overlap and entangle further, then the third relaxation mode due to the transient gel network originated from the aggregation of the clusters in the concentrated solution was observed. On the other hand, the relative amplitudes of middle and slow modes for semi-dilute solutions decrease with increasing temperature. At a temperature of about 508C, only a broad relaxation mode was observed indicating that intermolecular aggregation is disintegrated with increasing temperature, but the intramolecular aggregation of an isolated chain still exists due to the poor affinity of DOA to PVC chains in this temperature region. The poor solubility of the solvent used should be more favorable to the intramolecular aggregation of PVC chains, resulting in comparatively complex dynamic behaviors in semi-dilute solutions. q 2000 Elsevier Science Ltd. All rights reserved.