Molecular dynamics in hydrated sodium alginate by quasielastic and elastic neutron scattering

We present the QENS measurements result obtained at LLB using the MIBEMOL-TOF neutron spectrometer devoted to the study of sodium alginate-heavy water molecular dynamics behaviour, in an observation time range of 15 ns-1 ps. The data analysis allowed us to reveal the molecular motion manner of the two components of the system, as well as the dynamical parameters associated with various types of diffusion performed by water molecules constrained to move in the confined spaces created by the biopolymer chains. The various molecular groups belonging to these chains perform, at their turn, rotational diffusion motions in restricted spaces that can be described in terms of jump diffusion in a spherical potential model. From the elastic intensity we have calculated the elastic incoherent structure factor, EISF which reveals a molecular diffusion motion in spherical potential. At the same time we have obtained the mean square displacement (MSD), which is an increasing function of temperature presenting two slope changes at 145 and 185 K, respectively. These transition temperatures were associated with the molecular rotations release and translation outset, respectively.