Tribological Properties of Poly(methyl methacrylate) Brushes Prepared by Surface-Initiated Atom Transfer Radical Polymerization

Abstract

ABSTRACT:Surface-initiated living radical polymerization of methyl methacrylate (MMA) using copper/bipyridyl complex was carried out from silicon wafer immobilized with a 2-bromoisobutylate moiety, resulting in the assembly of polymer chains tethered by one end to a surface, a so-called ''polymer brush''. The thickness of the PMMA brush, which was estimated by ellipsometry and atomic force microscopy, increased linearly with the molecular weight of the chains, and was controlled by the free initiator concentration. The graft density of the PMMA brushes was estimated to be as high as 0.56 chains/nm 2 . The frictional properties of the high density PMMA brush were characterized by sliding the stainless ball probe on its surface across a width of 20 mm at a rate of 90 mm/min under loading of 0.49 N in air at room temperature. The PMMA brush was found to have a lower frictional coefficient and much better wear resistance than the corresponding spin-coated PMMA film because of the anchoring of the chain ends in the brush. In addition, the friction coefficient of the polymer brush significantly decreased in response to soaking in acetone and toluene, and increased in response to immersion in hexane. The tribological properties depended on the solvent quality.

Precise surface structure control of inorganic solid and metal oxide nanoparticles through surface-initiated radical polymerization

“…Furthermore, most previous research on the friction of grafted polymers has been carried out at very low normal force conditions, which are quite different from practical conditions. The authors have previously synthesized high-density PMMA brush on a flat silicon substrate [38] and have found that polymer brush affords a lowfriction and wear-resistant surface under a high normal load [39]. Therefore, hydrophilic polymer brush can be expected to give a low friction surface under wet conditions.…”

Molecular Aggregation State of Surface-grafted Poly{2-(perfluorooctyl)ethyl acrylate} Thin Film Analyzed by Grazing Incidence X-ray Diffraction

“…One possible method to overcome this weak adhesion is the immobilization of fluorinated polymer onto the substrate. Actually, spin-cast films are easily scratched out by friction or rubbing, though the tethered polymer surface shows good wear resistance 12 because the polymer chain ends are covalently bound with substrate. Polymer chains tethered to a surface or interface with a sufficiently high grafting density are referred to as ''polymer brush.''…”

Construction of Various Self-assembled Films and Their Application as Lubricant Coatings

“…Generally speaking, the immobilization of initiators is achieved by forming initiator-containing SAMs on the substrate. For instance, Takahara et al has prepared covalently tethered poly(methyl methacrylate) (PMMA) brushes on the Si wafer immobilized with an initiator SAMs of 2-bromoisobutylate moiety, abridged as DMSB (Fig. www.intechopen.com 19a) (Sakata et al, 2005). Compared with the spin-coated PMMA film, the self-assembled PMMA brush is found possessing much better wear resistance (Fig.…”