STRUCTURAL AND OPTICAL CHARACTERIZATION OF PMMA SURFACE TREATED IN LOW POWER NITROGEN AND OXYGEN RF PLASMAS

Oxygen and nitrogen plasmas are used to modify the Poly methyl methacrylate (PMMA) polymer surface and results are compared. Samples are treated in a plane parallel capacitively coupled RF discharge at 13.56 MHz frequency and 25 W power for different times. The modified surfaces are characterized by Fourier transform infrared spectrometer (ATR-FTIR) and atomic force microscopic (AFM) micrographs. By the results of contact angle measurement, polar and disperse parts of surface energy are observed. Real and imaginary parts of refractive index and dielectric constant for different samples are calculated using the transmission and reflection spectrum of samples and the energy gaps are calculated. RMS roughness of samples surface is found to be changed more effectively by nitrogen plasma compare to oxygen plasma but the molecular structure of the treated surfaces is noticeably affected by oxygen plasma. The contribution of the polar part of surface energy is decreased with treatment time. The water contact angle is decreased noticeably by this treatment while the energy gap of samples is not changed.