Functionalization of Poly(ethylene terephthalate) Film by Pulsed Plasma Deposition of Maleic Anhydride

Poly(ethylene terephthalate) (PET) films have been functionalized with carboxyl groups by pulsed plasma polymerization of maleic anhydride (MA). The preserved anhydride groups of MA were converted to carboxyl groups by subsequent hydrolysis. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to determine the chemical composition of the deposited MA plasma polymers. Atomic force microscopy (AFM) observations visually confirmed the coverage of the PET surface with plasma polymers after water treatment of the processed PET substrate, and the functionality in the XPS spectra of samples before and after water treatment indicated the persistence of functional groups and the good adhesion of the deposited layers on the PET substrate. In accordance with FTIR and XPS results, the density of carboxyl groups increased with decreasing plasma duty cycle. Compared with the pristine PET substrate, a higher roughness was observed on the modified PET surface by AFM. The roughness decreased sharply with decreasing plasma duty cycle