Control of a wetting transition by substrate surface chemistry: The interplay of long- and short-range forces

Using a capillary rise technique, we have explored the wetting of borosilicate glass surfaces by a polar + nonpolar liquid mixture of nitromethane + carbon disulfide for a series of surface preparations in which we replace polar hydroxyl groups with nonpolar methyl groups. Besides finding a Cahn transition of incomplete to complete wetting we have discovered circumstances under which this transition is suppressed, at least to within 1.0 K of the critical mixing point. We offer the following interpretation for this last result: a long-range substrate-liquid interaction which is unfavorable to wetting by the carbon disulfide--rich phase.