In this study, we investigated the low friction mechanism of a diamond-like carbon (DLC) film heated by laser irradiation in a nitrogen gas environment. The friction coefficient decreased from 0.5 to 0.06 when the contact area was heated to 250 °C. Subsequently, we heated the DLC film under non-contact conditions (2 μm distance between DLC film and pin surface) and collected the liquid materials adhered on the pin surface. The adhered materials were revealed to be hydrocarbons with -CH 2 -main-chains, as observed using Raman spectroscopy. On the other hand, thermal desorption gas chromatography with mass spectrometry using helium as a carrier gas demonstrated that hydrocarbons such as alkenes and alkanes with relatively high molecular weight were generated from heated DLC. This agreement between the results of the two analysis techniques suggested that the hydrocarbons in the liquid phase at room temperature were generated from the DLC film heated to a high temperature over 250 °C in an inert gas atmosphere. In addition, we confirmed the reduction in the friction coefficient after pre-heating a different location, as well as the dependence of the friction coefficient on the sliding velocity. The results suggest that hydrocarbons (e.g., alkenes or alkanes) generated upon DLC heating could possibly act as a lubricant to reduce the friction coefficient.

It is well known that a simple equation of theis of general applicability in describing the relationship between intrinsic viscosity and molecular weight for a wide range of polymeric substances. The values for the constants K , and a have been obtained for a number of polymer-solvent pairs, and eq. (1) has been used widely for the determination of molecular weights of high polymers. This relation is empirical in origin and its theoretical basis remains an unsettled question. With a few exceptions, however, the theoretical expressions obtained by Flory and Fox' can be approximated quite closely by this simple equation.The purpose of this note lies in demonstrating that there exists a specific relationship between K , and a, and that this relationship can be derived theoretically. The result furnishes not only some suggestions for the improvement of recent theories on intrinsic viscosity, but also useful information concerning molecular heterogeneity and chain configurations of polymer molecules.When the values of K , for a series of wellfractionated polymer homologs in various solvents (mixed or pure are plotted against the corresponding values of a, relationships such as those shown in Figure 1 are obtained. Similar relationships are found for the solutions in a single solvent of a series of fractionated polymer samples (for instance, polyvinyl chlorides or polybutadieneg) polymerized under different conditions.

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