Transport Properties of Phase-Separated Agarose Gel Department

Transport Properties of Phase-Separated Agarose Gel
Department of Physics, Graduate School of Science, Kyusyu University
6-10-1 Hakozaki, Fukuoka, 812-8581 Fukuoka, Japan
Yasuhiro Yamashita, Miho Yanagisawa, and Masayuki Tokita
Aqueous solution system of agarose shows a complicated phase behaviors. The
solution firstly transforms into the gel state from its solution state by the cooling of the
solution. The phase separation, then, occurs in the gel state of agarose through the
spinodal decomposition. The resultant gel, thus, obtained becomes opaque considerably
due to the critical opalescence from the density fluctuations. It indicates that the
structure of the polymer network of agarose gel becomes non-uniform due to the
spinodal decomposition. It may be natural to expect that the macroscopic properties of
the gel, such as the mechanical and the thermal properties, are influenced by the
presence of the spatial density fluctuations within the gel.
In this study, we discuss the influence of spinodal decomposition on the friction
between the solvent and the polymer network. The water flow through the polymer
network when a small pressure, P, is applied to the solvent. Then the velocity of the
water that flows in the gel, v, is expressed by the Darcy’s law as follows.
Here, L is the thickness of the gel, and f the friction coefficient between the solvent and
the polymer network of the gel.
We have measured the friction coefficients of agrose gels that are prepared
under various conditions. We also determined the correlation length of the frozen-in
density fluctuation by the small angle light scattering measurements. Then, the
relationship between the correlation length and the friction coefficients of the gel is