The paper describes experiments where thin films of polymers are deposited on smooth rigid substrates and rigid smooth sliders are slid over the organic films. The influence of temperature and pressure on the interfacial shear properties of a range of poly n-alkyl methacrylates is presented. The behavior of these materials is compared with that of polythenes. The effect of progressively increasing the length of the hydrocarbon side chain moiety in the methacrylates is investigated; the behavior of the polythenes is regarded as the limiting case for infinitely long hydrocarbon side chains.