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

Tokita, Masayuki; Uwataki, Mamoru; Yamashita, Yasuhiro; Hara, Takemi; Yanagisawa, Miho · Soft Matter · 2023

basic_science · Level V

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Abstract

We studied the friction coefficient between the polymer gel network and water <i>f</i> for thermoreversible agarose gels under various conditions of agarose concentration and gelation temperature. Since agarose gels exhibit phase separation below the gelation temperature, <i>f</i> strongly depends on the thermal history. We found that the friction coefficient of the phase-separated agarose gel normalized by the water viscosity, <i>f</i>/<i>η</i>, is expressed as <i>f</i>/<i>η</i> = <i>S</i>/<i>ξ</i>νSD where <i>ξ</i><sub>SD</sub> is the frictional pore size and <i>ν</i> and <i>S</i> are constant parameters. <i>ξ</i><sub>SD</sub> corresponds to the correlation length of the frozen density fluctuations of the polymers <i>via</i> spinodal decomposition determined from small-angle light scattering. The least-squares analysis of the results shows that the exponent is <i>ν</i> ≃ 2 with the numerical constant of <i>S</i> ≃ 10<sup>5</sup>/2π. The results suggest that the frictional properties of phase-separated agarose gels are dominated by the dilute regions of the bicontinuous gel structure.