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

In this work, the aggregation behavior of polyvinyl chloride/dioxane (PVC/D OA) solution was discussed through light scattering and viscometric measure ments. From the static light scattering results, PVC/DOA solution has a neg ative value of the second virial coefficient, A(2) value(ca. -3.65 x 10(-4) cm(3) mol g(-2)) at 30 degrees C, 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 re gions by increasing the concentration of PVC. In the infinite dilution regi on, [eta]C < 1, the single relaxation mode is considered related to the tra nslational diffusion of the individual PVC coil. In the hydrodynamic screen region, 1 < [eta]C < 4, the relaxation time distribution was divided into two major relaxation modes; i.e. the fast mode resembled that of the indivi dual PVC coil in the dilute solution, and the slow mode is considered relat ed to the cluster formed from the aggregation of several individual coils. At higher concentrations, [eta]C > 4, the polymer coils start to overlap an d entangle further, then the third relaxation mode due to the transient gel network originated from the aggregation of the clusters in the concentrate d solution was observed. On the other hand, the relative amplitudes of midd le and slow modes for semi-dilute solutions decrease with increasing temper ature. At a temperature of about 50 degrees C, only a broad relaxation mode was observed indicating that intermolecular aggregation is disintegrated w ith increasing temperature, but the intramolecular aggregation of an isolat ed 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 co mparatively complex dynamic behaviors in semi-dilute solutions. (C) 2000 El sevier Science Ltd. All rights reserved.