Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettabilitiy. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x10–3 m s-1 under normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. Poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained relatively low friction coefficients around 0.13 under humid air (RH&gt;75%) even after 200 friction cycles. The poly(SPMK) brush revealed a significantly low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to a good affinity of poly(SPMK) brush against water forming a water lubrication layer, and electrostatic repulsive interaction among the brushes bearing sulfonic acid groups. Furthermore, poly(SPMK-co-MTAC) brush with chemically cross-linked structure showed stable low friction coefficient in water even after 1400 friction cycles under the normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of brush layer.

Tribological properties of polyelectroryte brushes in water

2019 Fall National Meeting

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