Line tension approaching a first-order wetting transition: Experimental results from contact angle measurements

The line tension values of n-octane and 1-octene on a hexadecyltrichlorosilane coated silicon wafer, are determined by contact angle measurements at temperatures near a first-order wetting transition T(w). It is shown experimentally that the line tension changes sign as the temperature increases toward T(w) in agreement with a number of theoretical predictions. A simple phenomenological model possessing a repulsive barrier at l(0)=5.1+/-0.2 nm and a scale factor of B=78+/-6 provides a quantitative description of the experiments.