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The Influence of Shearing Parameters on the Frictional Forces Measured Between Polymer Brushes



Aaron M. Forster, S. M. Kilbey


Polymer brushes have potential as end-tethered lubricants. Brush layers immersed in a good solvent must be compressed to ~16% of their equilibrium height before friction forces are measured. The same experiment in a solvent near the theta temperature will produce friction forces just as the brushes first begin to interact. At this time, there is no definitive understanding of how these layers dissipate friction. The focus of this research is to understand the origins of friction between sliding brush layers. We have measured the normal and friction forces between three different molecular weight polystyrene brushes formed from polystyrene-polyvinylpyridine (PS-PVP) diblock copolymers using the surface forces apparatus (SFA). The experiments were conducted in toluene at 32 C (good solvent for PS), and cyclohexane (theta solvent at 34 C) at 32, 40, and 50 C. Shearing was initiated by oscillating one brush layer past an opposing layer using a triangular wave signal (steady sliding).We have previously shown that the ability of a polymer brush layer to dissipate friction forces increases with solvent temperature. Despite the improvement in friction dissipation, the normal force profiles between the layers remain relatively unchanged. As a further analysis of the friction experiments we discuss the role of shearing parameters, such as frequency and amplitude of oscillation, on the friction force measured during an experiment.
ACS PMSE Preprint


diblock copolymers, friction, polymer brushes, solvent quality, surface forces apparatus


Forster, A. and Kilbey, S. (2003), The Influence of Shearing Parameters on the Frictional Forces Measured Between Polymer Brushes, ACS PMSE Preprint, [online], (Accessed May 24, 2024)


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Created January 1, 2003, Updated February 19, 2017