Chain length effect on dynamical structure of poly (vinyl pyrrolidone)-polar solvent mixtures in dilute solution of dioxane studied by microwave dielectric relaxation measurement

Abstract

Dielectric relaxation study of the binary mixtures of poly(vinyl pyrrolidone) (PVP) (Mw = 24000, 40000 and 360000 g mol −1 ) with ethyl alcohol (EA) and poly(ethylene glycol)s (PEGs) (Mw = 200 and 400 g mol −1 ) in dilute solutions of dioxane were carried out at 10.1 GHz and 35 • C. The relaxation time of PVP-EA mixtures was interpreted by the consideration of a wait-and-switch model in the local structure of selfassociated ethyl alcohol molecules and also the PVP chain length as a geometric constraint for the reorientational motion of ethyl alcohol molecules. The formation of complexes and effect of PVP chain length on the molecular dynamics, chain flexibility and stretching of PEG molecules in PVP-PEG mixtures were explored from the comparative values of dielectric relaxation time. Further, relaxation time values in dioxane and benzene solvent confirm the viscosity independent molecular dynamics in PVP-EA mixtures but the values vary significantly with the non-polar solvent environment.

Synthesized tissue‐equivalent dielectric phantoms using salt and polyvinylpyrrolidone solutions

“…PVP phantom properties are expected to be influenced by molecular weight, for which a wide range is readily available. This extra degree of freedom could offer the opportunity to tune dielectric parameters in addition to other properties such as viscosity .…”

Theoretical and Experimental Investigation on the Solid Solubility and Miscibility of Naproxen in Poly(vinylpyrrolidone)

“…36,42 The effect of chain length on the dynamic structure of PVP and PEG mixtures in a polar solvent has been conferred in terms of its contribution to relaxation processes, its change in complexation density in a mixture and its segmental motion. 42 However, the influence of the PVP chain length on the estimated solubility and interaction parameter values could not be revealed by this methodology. This could be due to the inappropriate use of the FH model or the assumptions made in deriving the expressions as discussed earlier.…”

“…Though the interaction parameter looks more realistic as calculated from data at ambient temperature and with the drug composition at its solubility limits, its composition dependence cannot be worked out by this methodology. Based on the chemical structure of the drug substance, the chain length of PVP is crucial in deciding the interaction based miscibility. , The effect of chain length on the dynamic structure of PVP and PEG mixtures in a polar solvent has been conferred in terms of its contribution to relaxation processes, its change in complexation density in a mixture and its segmental motion . However, the influence of the PVP chain length on the estimated solubility and interaction parameter values could not be revealed by this methodology.…”

A simple head‐sized phantom for realistic static and radiofrequency characterization at high fields

“…The shell was filled using an aqueous solution of 76 g polyvinylpyrrolidone (PVP10, Sigma Aldrich, the Netherlands) with 1.78 g sodium chloride (NaCl) per 100 g of demineralized water, to reach the desired dielectric properties . We note that the recipe of this solution differs from the recipe reported in Ianniello et al due to the difference in polymer chain length of the polyvinylpyrrolidone compound . The solution was finally gelled using 1.5% (w/w) agarose (A9539, Sigma Aldrich, the Netherlands) to reduce thermal convection.…”

“…27 We note that the recipe of this solution differs from the recipe reported in Ianniello et al 27 due to the difference in polymer chain length of the polyvinylpyrrolidone compound. 31 The solution was finally gelled using 1.5% (w/w) agarose (A9539, Sigma Aldrich, the Netherlands) to reduce thermal convection.…”