Tribological properties of hydrophilic polymer brushes

The hydrophilic polymer brushes consisted with poly(2,3-dihydroxypropyl methacrylate) (poly(2)) and poly(2-methacryloyloxyethyl phosphorylcholine) (poly(3)) were prepared by surface-initiated ATRP of (2,2-dimethyl-1,3-dioxolan- 4-yl)methyl methacrylate (1) and 3 on the initiator-immobilized silicon wafer. Frictional properties of the poly(2) and (3) brushes were characterized by sliding a glass ball probe on the polymer brush surfaces in air and water under the load of 0.49 N at a sliding rate of 90 mm/min. Friction coefficient of poly(3) brush was lower than that of poly(2) in water. Further low friction coefficient was observed, even in air, by sliding a glass ball immobilized with poly(3) brush on the surface of poly(3)-immobilized silicon wafer even in air.