Surface and chemical characterization of PolyLA thin films fabricated using plasma polymerization

Abstract

Polymer thin films derived from the essential oil of Lavandula angustifolia (LA) are fabricated using plasma polymerization, and their surface and chemical characteristics investigated. The surface morphology of the polyLA films is examined using an atomic force microscope (AFM). The polymer is found to be uniform and pinhole free, and the average roughness of the films is found to be less than a nanometer and independent of the RF power employed during fabrication. Fourier transform infrared (FTIR) spectroscopy analysis of the polyLA film is performed. Comparison of the FTIR spectra for polyLA film with that of the starting monomer demonstrates that many of the original functional groups are retained during the polymerization process. Bands assigned to C==C stretching are lost due to their participation in the polymerization reactions. With increased RF power employed during fabrication, a decrease in intensity of most of the remaining bands in the FTIR spectra for the polyLA films is found. This is attributed to reactions such as dehydration of hydroxyl, cyclization, and aromatization associated with alkenes. In addition, it is found that the duration of exposure to UV irradiation and ion bombardment has an insignificant effect on the chemical structure of the polyLA film. Nuclear magnetic resonance (NMR) spectra of the polymer fabricated at low RF power reveals the presence of aromatics in the chemical structure. Water contact angle measurements demonstrate that the polyLA films range from mildly hydrophilic to mildly hydrophobic, and are stable while in contact with water.