SYNTHESIS AND CHARACTERIZATION OF SURFACE-FUNCTIONALIZED 1,2-POLYBUTADIENE BEARING HYDROXYL OR CARBOXYLIC-ACID GROUPS

We have modified the surface of 1,2-polybutadiene (PBD), without severe etching, via oxidation with aqueous potassium permanganate. The primary-functionality introduced, either hydroxyl or carboxylic acid groups, depends upon the concentration and temperature of the oxidizing solution. An alternative and more selective method for introducing hydroxyl or carboxylic acid moieties at this surface is the photolytic addition of 3-mercaptor-1,2-propanediol or mercaptoacetic acid, using benzophenone as an initiator and light (350 nm). The surface-modified polymer films were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-infrared (ATR-IR) spectroscopy, scanning electron microscopy (SEM), and the measurement of solid/liquid contact angles. On the polymer surfaces containing carboxylic acid groups, contact angles varied with the pH of the contacting drop of water, consistent with the presence of ionizable functionality. Surfaces bearing 1,2-diol groups showed no spectroscopic evidence for carboxylic acid groups and had Little or no dependence of contact angles on pH. Scanning electron microscopy revealed no gross topographical changes at the surface of PBD after any of these chemical derivatizations, except for samples treated for extended periods of time on a concentrated permanganate solution.