Continuum Monte Carlo simulations at constant pressure are performed on short chain molecules at surfaces. The rodlike chains, consisting of seven effective monomers, are attached at one end to a flat two dimensional substrate. It is found that the model exhibits phases similar to the liquid condensed and liquid expanded phases of Langmuir monolayers. The model is investigated here for a wide range of pressures and temperatures using a special form of constant pressure simulation compatible with the symmetry breaking during tilting transitions in the liquid condensed phases. At low pressures, the chains undergo a tilting transition exhibiting tilt directions towards nearest and also next nearest neighbors depending on temperature. At elevated temperatures and low pressure the film enters a fluidlike phase similar to the liquid expanded phase observed in experiment.