Epitaxial growth of solution grown polyvinylchloride (PVC) films

Abstract

Thin films of polyvinylchloride (PVC) have been grown epitaxially from three different solvents onto the (001) plane of rocksalt crystals by the isothermal immersion technique. The ranges of values of the growth parameters (temperature and concentration of the solution and immersion time) over which epitaxial growth is obtained have been established in each case. Films grown from a benzene and acetone mixture show epitaxy only at temperatures of 58°C or more and with concentrations below 0.1 g/100 ml. The epitaxial relation is (010) [110]_PVC(001) [110]_NaCl. The crystallites in the epitaxial films are of pyramidal shape and the molecular chains are folded in a direction perpendicular to the substrate. Films grown from ethyl methyl ketone solution show epitaxy only at temperatures of 65°C or more for concentrations greater than or equal to 0.15 g/100 ml. Films grown from cyclohexanone solution show epitaxy over a wide range of temperatures and concentrations. The epitaxial relation is (001) [110]_PVC(001) [110]_NaCl and the crystallites are rod- or fibre-like. The molecular chains in these crystallites are folded in a direction parallel to the substrate. Our studies show that epitaxial growth occurs in the earliest stage of growth of the films and further growth results in a mixture of amorphous and polycrystalline regions. The mechanism of epitaxial growth is explained in terms of our model for the growth of polymer chains. Two possible configurations of the molecular chains in the unit cell of PVC on a (001) rocksalt surface are proposed to explain the two epitaxial orientation relations observed.