Physical gels from poly(vinyl chloride): behaviour with concentration and temperature of aggregates formed in dilute solutions

Aggregates formed in dilute poly(vinyl chloride) (PVC) solutions (i.e. below the critical gel concentration) have been studied by static and quasielastic light scattering as well as by viscometry as a function of the polymer concentration and the temperature. From the results, it is concluded that two types of physical links exist in these aggregates: ‘strong’ links that persist up to 62°C and ‘weak’ links that progressively break up with temperature. Further, the weak links are absent in aggregates prepared at the lowest concentrations ( C ≤ 0.5 × 10 −2 g cm −3) but appear at the highest concentrations ( C ≥ 1 × 10 −2 g cm −3). These results are discussed and the conclusions are extrapolated to the gel state. In particular, it is suggested that the weak links are responsible for the physical ageing of PVC thermoreversible gels.