Abstract
The surface sliding friction of chemically cross-linked poly(dimethyl siloxane) (PDMS) swollen with linear PDMS as an oligomer is investigated. The friction force f increases with the normal pressure P in a power-law relation f∝P α, where the exponent α changes in a range of 0-1, depending on the degree of polymerization, N poly, of the linear PDMS oligomer. When N poly is in a range of 240-320, a dramatic decrease in friction force is observed at a critical normal pressure, P c, leading to a very low friction coefficient on the order of 10−3 at high-pressure ranges. The P c increases with decreasing network size N netof the gel and also with increasing polymer length related to N poly. One possible explanation for this transition phenomenon in friction is that linear PDMS molecules are exuded from the gel network beyond a certain pressure and behave as polymer brushes, which are able to reduce the friction.
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Tada, T., Kaneko, D., Gong, J.P. et al. Surface Friction of Poly(dimethyl Siloxane) Gel and Its Transition Phenomenon. Tribology Letters 17, 505–511 (2004). https://doi.org/10.1023/B:TRIL.0000044498.60673.76
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DOI: https://doi.org/10.1023/B:TRIL.0000044498.60673.76