Plasma-Induced Graft Polymerization of Acrylic Acid onto Poly(ethylene terephthalate) Films: Hydrophilic Modification

A complete and permanent hydrophilic modification of poly (ethyleneterephthalate) (PET) films is achieved by argon-plasma irradiation, subsequently grafting acrylic acid (AA) in vapor phase onto their surface. Both Ar plasma irradiation alone and post grafting AA rendered a complete hydrophilicity to PET surfaces. However, the hydrophilicity of the PET surface, only treated with the Ar plasma, is not permanent. In contrast, PET films, irradiated by the Ar plasma, exposed to air, and subsequently grafted with AA monomer, are permanently hydrophilic. Degradation of polymer chains on the plasma-irradiated surface is proportional to time of exposure. Electron spectroscopy for chemical analysis (ESCA) confirmed the grafting of AA onto the film surface, which results in a large amount of incorporated oxygen-containing functional groups like carboxylic (O C = O) and carbonyl (C = O). The morphology of grafted surfaces, observed by scanning electron microscopy (SEM), displays some large area of microporosity compared to relative smooth morphology of the control one. Grafted functional groups and surface microporous structure are the main factors to enhance hydrophilicity of the PET films.