Morphologies of Various Polycaprolactone/Polymer Blends in Ultrathin Films

Morphologies of ultrathin films of nine poly(epsilon-caprolactone)/polymer miscible and immiscible binary blends have been investigated under isothermal crytallization conditions by real. time atomic force microscopy, Optical microscopy, and electron diffraction techniques. It was found that the truncated lozenge-shape morphology of the pure poly(epsilon-caprolactone) (PCL) crystals is modified in miscible blends, forming regular or inverted S- or C-shaped crystals, the Curvature, depending on the nature of the second polymer and increasing with blend composition. Moreover, the growth rate decreases with the addition of the second polymer following the same order as the crystal curvature: PVC > CPE(48%) > SAN(25%) > PC > SAN(9.5%) > PVME. In contrast, for immiscible blends, no significant changes in kinetics and morphology were observed since a constant crystal growth rate and the same truncated lozenge-shape morphology as pure PCL crystals are obtained at all compositions. Kinetic and morphological changes in miscible blends are discussed in terms of PCL/polymer intermolecular interactions since the growth rate decreases and the curvature increases with the addition of polymers of increasing interactions.