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 hexadecyltrichlorosil ane coated silicon wafer, are determined by contact angle measurements at t emperatures near a first-order wetting transition T-w. It is shown experime ntally that the line tension changes sign as the temperature increases towa rd T-w in agreement with a number of theoretical predictions. A simple phen omenological 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 t he experiments.