Percolation models of free and bound water under the influence of nearest neighbour interactions

Water Dynamics in Physical Hydrogels Based On Partially Hydrophobized Hyaluronic Acid

“…Reorientational motions on similar time-scales have been observed in NMR measurements for oligomers of HYA in solution at 298 K. 38 They have been interpreted in terms of a superposition of a rotational tumbling of the molecule around the β-1,4−β-1,3 vector and of a local reorientation of the C−H bond. 38−40 It is noteworthy that, in our experiment, owing to the D−H isotopic exchange that mostly occurs in hydroxyl groups, the signal from the HYA matrix is predominantly due to the same chemical groups observed in 13 C NMR relaxation.…”

“…Polysaccharide-based hydrogels are relatively stable even at very low saccharide concentration (down to 1% and less). Water may act also as a “plasticiser”, inducing some degree of alignment of the saccharide units and, thus, affecting not only the conformation but also the dynamical properties at a molecular level. , Experimental results, together with data from computer simulations, have confirmed that water bound to hydrophilic sites has relaxation times lengthened compared to bulk water, assigned to an increase in the hydrogen bond connectivity in the vicinity of a hydrophilic surface …”

“…11,12 Experimental results, together with data from computer simulations, have confirmed that water bound to hydrophilic sites has relaxation times lengthened compared to bulk water, assigned to an increase in the hydrogen bond connectivity in the vicinity of a hydrophilic surface. 13 The microscopic dynamical properties of polymer-and biopolymer-based gels may cover a large time window ranging from femto-to almost microseconds. Complementary spectroscopic techniques that can altogether cover most of this interval are: NMR, dielectric relaxation, quasielastic, (QENS), and inelastic (INS) neutron scattering.…”