LAYERING TRANSITIONS AND TRIBOLOGY OF MOLECULARLY THIN FILMS OF POLY(DIMETHYLSILOXANE)

摘要

When fluid molecules are confined between two solid walls, their dynamic properties are completely different from those of the bulk. Relaxation times of molecular motions are prolonged by many orders of magnitudes and the system behaves not like a fluid but exhibits solidlike features. One of the major origins of the solidlike responses is the layering of molecules parallel to solid walls. This layering effect has been reported by a number of authors, but the systems studied were limited to simple liquids. In this paper, we present the layering of poly(dimethylsiloxane) (PDMS) melt in a molecularly confined film [1,2]. This is the first observation, to the best of our knowledge, for a large and flexible polymer melt to form a discrete layer structure, obtained under the combination of compression and sliding motions.