Morphology-driven surface segregation in a blend of poly(epsilon-caprolactone) and poly(vinyl chloride).

A blend of poly(epsilon-caprolactone) (PCL) and poly(vinyl chloride) (PVC) with 90 wt % PCL was prepared. Two films of this blend, which were grown at 35 and 45 degrees C, showed the absence and presence of banded spherulites, respectively. A detailed examination conducted with time-of-flight secondary ion mass spectrometry (ToF-SIMS) found that the surface composition of the film grown at 45 degrees C was related to its structure, which was shown to contain ridges and valleys. Phase images obtained using atomic force microscopy (AFM) indicated that the ridges and valleys consisted of edge-on and flat-on lamellae, respectively. ToF-SIMS imaging revealed that PVC and PCL were located mainly on the surface of the valleys and ridges, respectively. This morphology-driven surface segregation was caused by the difference in the surface energy between the flat-on and edge-on lamellae.