AFM of poly(vinyl alcohol) crystals next to an inorganic surface

Crystallization of poly(vinyl alcohol) in the presence of an inorganic filler surface (sodium montmorillonite, MMT) was observed and compared to the crystallization of the neat polymer. For this purpose, several atomic force microscopy modes, providing spatial resolution between amorphous and crystalline polymer, are employed to observe filled and unfilled PVA films. The various AFM modes utilized are detailed, with the emphasis on how they can contrast stiff (crystalline) and softer (amorphous) domains on a polymer surface. The study revealed changes in the PVA crystal morphology, with bulk crystallites growing to sizes of more than 5 mum, whereas next to the inorganic surfaces grow to only 1-2 mum in size. Moreover, complementary X-ray diffraction and DSC investigations indicate a new crystal structure formed next to the MMT surfaces, at the expense of the bulklike crystal.