First-order and critical wetting of alkanes on water

Ellipsometry measurements of the wetting behavior of different alkanes on w ater show a sequence of two wetting transitions: a first-order (discontinuo us) transition followed by a critical (continuous) one. We report temperatu re-induced wetting transitions for different alkanes and a novel pressure-i nduced wetting transition for an alkane mixture. The experiments enable us to determine the global wetting phase diagram as a function of chain length and temperature which we subsequently calculate theoretically. The two tra nsition lines are found to be approximately parallel, in accordance with ba sic theoretical arguments.