Boundary lubrication with aqueous solutions of silicone-based amphiphilic block copolymer aggregates: effect of concentration

Autor: Naoyuki Yamazaki, Hikaru Kimura, Shunichi Watanabe, Takumi Miyamoto, Shinji Yamada
Rok vydání: 2021
Předmět:
Zdroj: Polymer Journal. 53:1123-1132
ISSN: 1349-0540
0032-3896
Popis: The thin film structures and tribological properties of aqueous solutions of a silicone-based amphiphilic block copolymer, bis-isobutyl polyethylene glycol (PEG)-14/amodimethicone (BIPA) copolymer, confined between mica surfaces were investigated using the surface forces apparatus. Measurements were made for three BIPA concentrations (0.005, 0.05, and 0.5 wt%); the effect of concentration on the structures and properties was evaluated. The BIPA molecules had positive charges in the solutions and formed an adsorbed layer on a negatively charged mica surface. The static hard-wall thicknesses were within the range of 3.3–5.6 nm for the three concentrations. Applying sliding motions under load L further decreased the thickness. The minimum dynamic thicknesses were 2.4–2.7 nm for the three concentrations, indicative of sliding between two adsorbed BIPA molecular layers. The friction coefficients were on the order of 10−5 for the three concentrations; extremely low friction was obtained originating from the slippage of the fluid-like water layer between the adsorbed layers. All three concentrations exhibited good lubricity, but precise comparison implies some differences in the film structures and friction mechanisms. The details of the differences were discussed from the perspective of the dissolution states of BIPA in the solutions and adsorbed/sliding conformations. The thin film structures and tribological properties of aqueous solutions of a silicone-based amphiphilic block copolymer confined between mica surfaces were investigated using the surface forces apparatus. Experiments were performed for three copolymer concentrations; the effect of concentration on the structures and properties was evaluated. All the concentrations exhibited good lubricity (friction coefficient on the order of 10−5). However, precise comparison between concentrations revealed some differences in the molecular friction mechanisms, which were discussed from the perspective of the dissolution states of copolymers in the solutions and adsorbed/sliding conformations.
Databáze: OpenAIRE
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