WATER DYNAMICS IN CHARGED AND UNCHARGED POLYSACCHARIDE GELS BY QUASI-ELASTIC NEUTRON-SCATTERING

Using a mu eV neutron spectrometer we have studied the mobility of wat er in gels formed by two polysaccharides: agarose and hyaluronic acid. Agarose is a nearly uncharged polysaccharide; its gels are fairly sti ff, quasi-random networks of fibre bundles. Hyaluronic acid is a highl y charged polysaccharide capable of retaining large amounts of water i n entangled meshworks with unusual theological properties. We have ana lysed sets of quasi-elastic lineshapes broadened by two proton populat ions with different degrees of freedom. The resulting microscopic mobi lity parameters and their temperature dependence reveal a complex beha viour. The overall effect of the biopolymer network is to increase tra nslational as well as rotational relaxation times, but the changes obs erved are not dramatic and cannot fully account for the strikingly dif ferent macroscopic properties of these gels. Local electrostatic inter actions (over 3 to 20 Angstrom) do not appear to influence significant ly the theological behaviour.