Frictional properties of phase-separated agarose hydrogels in water permeation.

We studied the friction coefficient between the polymer gel network and water for thermoreversible agarose gels under various conditions of agarose concentration and gelation temperature. Since agarose gels exhibit phase separation below the gelation temperature, strongly depends on the thermal history. We found that the friction coefficient of the phase-separated agarose gel normalized by the water viscosity, /, is expressed as / = /νSD where is the frictional pore size and and are constant parameters. corresponds to the correlation length of the frozen density fluctuations of the polymers spinodal decomposition determined from small-angle light scattering. The least-squares analysis of the results shows that the exponent is ≃ 2 with the numerical constant of ≃ 10/2π. The results suggest that the frictional properties of phase-separated agarose gels are dominated by the dilute regions of the bicontinuous gel structure.