Nanowear on polymer films of different architecture.

In this paper, we describe atomic force microscope (AFM) friction experiments on different polymers. The aim was to analyze the influence of the physical architecture of the polymer on the degree and mode of wear and on the wear mode. Experiments were carried out with (1) linear polystyrene (PS) and cycloolefinic copolymers of ethylene and norbornene, which are stabilized by entanglements, (2) mechanically stretched PS, (3) polyisoprene-b-polystyrene diblock copolymers, with varying composition, (4) brush polymers consisting of a poly(methyl methacrylate) (PMMA) backbone and PS side chains, (5) PMMA and PS brushes grafted from a silicon wafer, (6) plasma-polymerized PS, and (7) chemically cross-linked polycarbonate. For linear polymers, wear depends critically on the orientation of the chains with respect to the scan direction. With increasing cross-link density, wear was reduced and ripple formation was suppressed. The cross-linking density was the dominating material parameter characterizing wear.