WETTING PROPERTIES AND STABILITY OF SILANE-TREATED GLASS EXPOSED TO WATER, AIR, AND OIL

Wettability and stability of glass surfaces modified with five organosilanes were characterized by monitoring temporal changes in water-air contact angles on treated glass slides stored in air, water, and oil. Silane treatment altered the wetting properties of sodalime glass slides, with all contact angles exhibiting hysteresis. The induced hydrophobicity remained stable for slides stored in air and oil, but deteriorated for slides stored in water, as indicated by a decrease in advancing and/or receding contact angles. The critical surface tension, above which a liquid displays a finite contact angle on a surface, was not sensitive to aging. Quartz and silica substrates gave essentially the same results as sodalime glass. Bacterial action was ruled out as a primary cause of deterioration of hydrophobicity. A coating of refined oil (Soltrol 130) on the treated surface prolonged stability in water but eventual breakdown was still evident from decrease in the receding contact angles. Hydrolysis was the likely cause of deterioration. Water-Soltrol 130 advancing and receding contact angles were higher than water-air contact angles, but there was a systematic relationship between them. Recommendations are made as to the most suitable silanes for treating glass, quartz, or silica surfaces for investigations which last more than a few hours. © 1993 Academic Press, Inc.