Dynamic light scattering studies on poly(vinyl chloride) clusters and aggregates in tetrahydrofuran

A novel method to characterize the history of processing for poly(vinyl chloride) (PVC) has been presented. This method consists of: (1) dissolving PVC in tetrahydrofuran; followed by (2) dynamic light scattering (DLS); and (3) cluster-size distribution analysis. It was found that the characteristic decay time distribution function G(τ) showed the history of sample treatment, where τ is the characteristic decay time. In the case of dilute solutions of virgin PVC resin, G(τ) was dominated by the fast mode at τf≈30 μs. This is the first observation of the presence of PVC clusters of ca. 4.5–6.0 nm. On the other hand, those prepared from a milled PVC film exhibited another peak at a larger characteristic time, τs≈3 ms. This indicates that aggregates about 100 times larger than the clusters are formed during processing. The formation of the larger clusters was also verified by atomic force microscopy. It is concluded that DLS is a sensitive means in characterizing gel structure and processing history for PVC films.