Poly(vinyl alcohol) (PVA) hydrogels were prepared under different conditions such as the various concentrations

solvents

the times of freeze-thaw circles and the introduction of polyethylene oxide (PEO).Effect of these preparation parameters on the frictional behavior of PVA hydrogels sliding on a glass surface was investigated in detail.The results show that mixed solvent of water and dimethyl sulfoxide facilitates the formation of a more uniform gel network and thus increases the strength of hydrogels.Moreover

the strength of hydrogels can also be increased by increasing freeze-thaw circle times and adding ultrahigh molecular weight PEO due to the formation of a dense and uniform network.On the other hand

stiff hydrogels with high modulus show a higher frictional stress at a low sliding velocity compared with soft hydrogels; however

it is fast to get into the hydrodynamic lubrication and exhibits a lower frictional stress at a high sliding velocity.The velocity (10-1 ~100m/s) is approximately the cartilage sliding velocity of the knee when people are walking.In addition

PEO molecular brush can reduce the frictional stress of PVA sliding against glass at high sliding velocities to some extent

however

at low sliding velocities

the reducing of frictional stress depends on the concentration of the added PEO.It suggests that increasing the modulus of hydrogels is more effective in reducing the friction at high sliding velocity region than that of introducing PEO with ultrahigh molecular weight.