AFM studies on microtribology of concentrated polymer brushes in solvents

In concentrated polymer brushes (CPBs) prepared by surface-initiated living radical polymerization, graft chains in a good solvent are highly stretched, nearly to their full length, giving properties quite different and unpredictable from those of semi-dilute polymer brushes (SDPBs) previously studied. This paper reviews our recent studies on the microtribology of confronted CPBs in solvents. Atomic force microscopy revealed that the CPBs of poly(methyl methacrylate) and poly(styrene) showed dramatically low frictional coefficients in good solvents compared with those of the corresponding SDPBs. This was reasonably ascribed to confronted CPBs hardly mixing with each other due to their huge osmotic and elastic interactions. The lubrication mechanism of CPBs was discussed according to the sliding-speed dependency of frictional coefficient, and two different mechanisms, boundary and hydrodynamic lubrications, were suggested. Thermo-responsive lubrication was also demonstrated for the CPB of poly(N-isopropyl acrylamide). We believe that these studies will open up a new route to precision surface modification for "super" lubrication.

[1]  J. Klein.  Shear, Friction, and Lubrication Forces Between Polymer-Bearing Surfaces , 1996 .

[2]  P. Gennes,et al.  Rubber-rubber adhesion with connector molecules , 1992 .

[3]  P. G. de Gennes,et al.  Polymers at an interface; a simplified view , 1987 .

[4]  K. Matyjaszewski,et al.  Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization , 2003 .

[5]  Shinpei Yamamoto,et al.  Controlled Graft Polymerization of Methyl Methacrylate on Silicon Substrate by the Combined Use of the Langmuir−Blodgett and Atom Transfer Radical Polymerization Techniques , 1998 .

[6]  William J. Brittain,et al.  Polymer brushes : synthesis, characterization, applications , 2004 .

[7]  D. H. Napper.  Polymeric stabilization of colloidal dispersions , 1983 .

[8]  Shinpei Yamamoto,et al.  Surface Interaction Forces of Well-Defined, High-Density Polymer Brushes Studied by Atomic Force Microscopy. 1. Effect of Chain Length , 2000 .

[9]  Y. Cohen,et al.  A terminally anchored polymer chain in shear flow: Self-consistent velocity and segment density profiles , 1994 .

[10]  E. Kumacheva,et al.  Confinement-Induced Phase Transitions in Simple Liquids , 1995, Science.

[11]  T. Patten,et al.  Atom transfer radical polymerization from nanoparticles: a tool for the preparation of well-defined hybrid nanostructures and for understanding the chemistry of controlled/"living" radical polymerizations from surfaces. , 2001, Journal of the American Chemical Society.

[12]  Krzysztof Matyjaszewski,et al.  Synthesis and characterization of organic/inorganic hybrid nanoparticles: Kinetics of surface-initiated atom transfer radical polymerization and morphology of hybrid nanoparticle ultrathin films , 2003 .

[13]  H. Otsuka,et al.  Tribological Properties of Poly(methyl methacrylate) Brushes Prepared by Surface-Initiated Atom Transfer Radical Polymerization , 2005 .

[14]  E. Harth,et al.  New polymer synthesis by nitroxide mediated living radical polymerizations. , 2001, Chemical reviews.

[15]  T. Fukuda,et al.  Structure and properties of high-density polymer brushes prepared by surface-initiated living radical polymerization , 2006 .

[16]  M. Kawaguchi,et al.  Polymer adsorption at solid-liquid interfaces , 1992 .

[17]  W. Huck,et al.  Polymer brushes via surface-initiated polymerizations. , 2004, Chemical Society reviews.

[18]  T. Patten,et al.  Preparation of Structurally Well-Defined Polymer−Nanoparticle Hybrids with Controlled/Living Radical Polymerizations , 1999 .

[19]  J. Israelachvili.  Intermolecular and surface forces , 1985 .

[20]  T. Fukuda,et al.  Suspensions of Silica Particles Grafted with Concentrated Polymer Brush: Effects of Graft Chain Length on Brush Layer Thickness and Colloidal Crystallization , 2007 .

[21]  E. Harth,et al.  Production of crosslinked, hollow nanoparticles by surface‐initiated living free‐radical polymerization , 2002 .

[22]  A. Takahara,et al.  Synthesis and frictional properties of poly(2,3-dihydroxypropyl methacrylate) brush prepared by surface-initiated atom transfer radical polymerization , 2005 .

[23]  Timothy P. Lodge,et al.  Tethered chains in polymer microstructures , 1992 .