ABSTRACT
Tribometer .......................................................................... 117 6.3 Results and Discussion ................................................................................. 118
6.3.1 Preparation of Poly[1-(2-Methacryloyloxy)Ethyl-3Ethylimidazolium Chloride] Brush .................................................. 118
6.3.2 Frictional Properties of the PMIS Brush .......................................... 119 6.3.2.1 PMIS Brush versus Bare Silicon Wafer: Effect of
Sliding Velocity .................................................................. 119 6.3.2.2 PMIS versus PHMA Brush against Glass Ball: Effect
of Solvent ........................................................................... 121 6.3.2.3 Contact Angle Measurement ............................................. 123 6.3.2.4 PMIS versus PHMA Brush against Bare Glass: Effect
of Friction Cycles ............................................................... 123 6.3.3 Optical and XPS Surface Analyses .................................................. 123
Ionic poly[1-(2-methacryloyloxy)ethyl-3-butylimidazolium bis(triuoromethanesulfonyl)imide] (PMIS) and nonionic poly(n-hexyl methacrylate) (PHMA) brushes were prepared on silicon wafers with immobilized initiator by surface-initiated atom transfer radical polymerization. Macroscopic frictional properties of the brushes were characterized by a ball-on-plate-type tribometer under reciprocating motion in a dry nitrogen atmosphere, water, methanol, toluene, and 1-ethyl-3-methylimidazolium bis(triuoromethanesulfonyl) imide (EMImTFSI). EMImTFSI on PMIS brush showed much lower friction coefcients than on nonmodied silicon wafer in the speed range of 10−4-10−1 m s−1. It is attributed that the high afnity of the PMIS brush to EMImTFSI led to a reduction in the interaction between the brush and the friction probe, which resulted in a low friction coefcient. The friction coef-cient gradually decreased to 0.01 with increasing sliding velocity from 10−4 to 10−1 m s−1. The friction coefcient of the PMIS brush remained low until 800 friction cycles in the dry nitrogen atmosphere, while the PHMA brush was abraded away within 150 friction cycles. The x-ray photoelectron spectroscopy measurements of the worn surfaces on the PMIS brush indicated that the brush was gradually abraded away by friction but the brush structure still remained after 400 friction cycles.
