Cholestryl linoleate

The effect of temperature on friction between aluminum sheet (3004-H19) and 52100 steel balls due to the liquid crystal cholestryl linoleate (CL) and stearic acid (S A) was measured under boundary conditions on a modified MOFISS friction tester. Temperatures were selected so that the order of CL was cholestric (25 C), smectic (30 C) or isotropic (40 C). The results showed no temperature dependence on COF of CL. It is speculated that this lack of dependence might be due to dramatic shifts in phase-transition temperatures of the thin film LC from that of the bulk. 

To test this hypothesis, we investigated the effect of temperature on the friction properties of cholestryl linoleate (CL) under boundary conditions, and compart the results to a similar investigation of a well-known boundary additive, stearic acid (S A) which is not a liquid crystal. As shown in Figure 2, CL is crystalline below 20 C, smectic at 20-26 C, cholesteric at 26-35"C and isotropic above 35"C. CL was selected because its isotropic order is accessible at a relatively low temperature. 

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