Preparation and tribological behavior of silicone films doped with ionic liquid

The silicone films chemically modified with ionic liquids on single crystal Si and/or glass slide substrates with different terminals were prepared making use of spin-coating technique. The polymerization and/or crosslinking in the silicone film on vinyl-terminated substrate were examined by means of Fourier transformation infrared spectroscopy. The tribological properties of the films sliding against AISI-52100 steel ball in a ball-on-plate configuration were investigated using a dynamic static friction coefficient measurement apparatus. The morphologies of the wear tracks of bare substrate, the composite films, and the counterparts were observed using a scanning electron microscope. It was found that the composite films on the hydroxyl-terminated and methyl-terminated substrates showed poor tribological properties, while the films on the vinyl-terminated substrate exhibited excellent tribological behavior. It was presumed that there was chemical bond between the crossed-link film and the vinyl-terminated substrate, which contributed to increase the bonding strength between the composite films and the substrate and hence improved the friction and wear behavior of the composite films. The decrease of the friction coefficient at a large enough sliding velocity was related to the shear thinning effect of the composite film thereat.