Surface friction of hydrogels with well-defined polyelectrolyte brushes.
Hydrogels of poly(2-hydroxyethyl methacrylate) (PHEMA) with well-defined polyelectrolyte brushes of poly(sodium 4-styrenesulfonate) (PNaSS) of various molecular weights were synthesized, keeping the distance between the polymer brushes constant at ca. 20 nm. The effect of polyelectrolyte brush length on the sliding friction against a glass plate, an electrorepulsive solid substrate, was investigated in water in a velocity range of 7.5 x 10(-5) to 7.5 x 10(-2) m/s. It is found that the presence of polymer brush can dramatically reduce the friction when the polymer brushes are short. With an increase in the length of the polymer brush, this drag reduction effect only works at a low sliding velocity, and the gel with long polymer brushes even shows a higher friction than that of a normal network gel at a high sliding velocity. The strong polymer length and sliding velocity dependence indicate a dynamic mechanism of the polymer brush effect.
Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Yutaka
Y
Ohsedo
Rikiya
R
Takashina
Jian Ping
JP
Gong
Yoshihito
Y
Osada
D004573:Electrolytes / Q000737:chemistry*; D017276:Friction; D020100:Hydrogels / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D008970:Molecular Weight; D011102:Polyhydroxyethyl Methacrylate / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D004573:Electrolytes; D020100:Hydrogels; D011108:Polymers; D013451:Sulfonic Acids; D014867:Water; D011102:Polyhydroxyethyl Methacrylate; C077114:styrenesulfonic acid polymer