Polymer Dynamics in Glycerol-Water Mixtures.

Velocity correlation spectra (VAS) in binary mixtures of water and glycerol (G/W), obtained by measurements using the modulated gradient spin echo (MGSE) NMR method, were explained by the interactions of water molecules with clusters formed around the hydrophilic glycerol molecule, which drastically change the molecular dynamics and rheology of the mixture. It indicates a thickening of the shear viscosity, which could affect the dynamics of submerged macromolecules. The calculation of the polymer dynamics with the Langevin equations according to the Rouse model, where the friction was replaced by the memory function of the retarded friction, gave the dependence of the dynamics of the polymer on the rate of shear viscous properties of the solvent.

Molecular self-diffusion in internal magnetic fields of porous medium investigated by NMR MGSE method.

Inhomogeneous magnetic fields generated in porous media due to differences in magnetic susceptibility at solid/liquid interfaces and due to intrinsic or artificially doped magnetic impurities can be used to gain insight into the molecular dynamics of fluid in the structure of a porous medium using the concept of NMR modulated gradient spin echo method. We extended the theory of this method to the case of an inhomogeneous magnetic field that cannot be approximated by an uniform gradient, in order to explain the CPMG measurements of self-diffusion in water soaked ceramics, which are doped with magnetic impurities of different contents. The new interpretation provides the spin relaxation times, the average pore size and their distribution, as well as the strength of the internal magnetic gradient fields in the doped ceramics.

Diffusion Spectrum of Polymer Melt Measured by Varying Magnetic Field Gradient Pulse Width in PGSE NMR.

The translational motion of polymers is a complex process and has a big impact on polymer structure and chemical reactivity. The process can be described by the segment velocity autocorrelation function or its diffusion spectrum, which exhibit several characteristic features depending on the observational time scale-from the Brownian delta function on a large time scale, to complex details in a very short range. Several stepwise, more-complex models of translational dynamics thus exist-from the Rouse regime over reptation motion to a combination of reptation and tube-Rouse motion.

Study of translational dynamics in molten polymer by variation of gradient pulse-width of PGSE.

Pulsed gradient spin echo is a method of measuring molecular translation. Changing Δ makes it sensitive to diffusion spectrum. Spin translation effects the buildup of phase structure during the application of gradient pulses as well.