Spectroscopic studies of microwave plasma reactions of maleic anhydride on poly(vinylidene fluoride) surfaces: Crystallinity and surface reactions

These studies show that maleic anhydride and carboxylic acid groups can be chemically bonded to poly(vinylidene fluoride) (PVDF) surfaces with the use of microwave plasma energy. Maleic anhydride reacts with the PVDF surface through a C=C bond opening of the maleic anhydride ring, and its hydrolysis results in chemically attached carboxylic acid groups on the PVDF surface. The extent of the surface reactions can be monitored using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy. These studies also show that maleic anhydride C=O groups are preferentially parallel to the PVDF surface, and molecular mechanics force field calculations indicate that the most favorable angle between maleic anhydride and a polymer backbone is 25 degrees. Quantitative spectroscopic analysis shows that before hydrolysis, volume concentrations of maleic anhydride vary from 1.32 x 10(-5) to 7.94 x 10(-5) mg/cm(3) (surface concentrations from 1.8 x 10(-9) to 6.67 x 10(-9) mg/cm(2)), whereas the carboxylic acid content changes from 8.67 x 10(-5) to 2.7 x 10(-4) mg/cm(3) (1.18 x 10(-8) to 2.27 x 10(-8) mg/cm(2)) depending on the reaction conditions and depth from the surface. After hydrolysis, the carboxylic acid content changes from 9.1 x 10(-5) to 3.15 x 10(-4) mg/cm(3) (1.24 x 10(-8) to 2.65 x 10(-8) mg/cm(2)).