title: Frictional properties of a polycationic brush.
abstract: The frictional behaviour of end-grafted poly[2-(dimethyl amino)ethyl methacrylate] films (brushes) has been shown by friction force microscopy to be a strong function of pH in aqueous solution. Data were acquired using bare silicon nitride and gold-coated tips, and gold coated probes that were functionalized by the deposition of self-assembled monolayers. At the extremes of pH (pH = 1, 2, and 12), the friction-load relationship was found to be linear, in agreement with Amontons' law of macroscopic friction. However, at intermediate pH values, the data were fitted by single asperity contact mechanics models; both Johnson-Kendall-Roberts (JKR) and Derjaguin-Muller-Toporov models were observed, with JKR behaviour fitting the data better at relatively neutral pH.
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK. mark.geoghegan@sheffield.ac.uk.
authors.forename: Maryam
authors.initials: M
authors.lastname: Raftari
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Zhang
authors.forename: Steven R
authors.initials: SR
authors.lastname: Carter
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Leggett
authors.forename: Mark
authors.initials: M
authors.lastname: Geoghegan
mesh_terms: D006863:Hydrogen-Ion Concentration; D008689:Methacrylates / Q000737:chemistry*; D009757:Nylons / Q000737:chemistry*; D011073:Polyamines / Q000737:chemistry*; D000071228:Polyelectrolytes
chemical_list: D008689:Methacrylates; D009757:Nylons; D011073:Polyamines; D000071228:Polyelectrolytes; C407037:poly(2-(dimethylamino)ethyl methacrylate)