Influence of the Solvent Environment on the Contact Mechanics of Tip-Sample Interactions in Friction Force Microscopy of Poly(ethylene terephthalate) Films

摘要

Friction force microscopy measurements have been carried out on free-standing films of poly(ethylene terephthalate) in a variety of different media.In ethanol,the adhesion force was small,and the friction-load relationship was linear.In perfluorodecalin,nonlinearity was observed in the friction-load relationship,and the data have been found to fit the Johnson-Kendall-Roberts model of contact mechanics.The behavior in hexadecane was also characterized by a single-asperity contact model,but in this case,the data were found to fit the Derjaguin-Muller-Toporov model.It is suggested that these differences are due to the different strengths of tip-sample adhesion,which arise from the differences in the dielectric constants of the media:in ethanol,which has a high dielectric constant,the friction force varies linearly with the load,whereas in media of low dielectric constant,adhesion-limited behavior is observed.