Molecular Dynamics and Hydration Behavior of Aqueous Polyvinylpyrrolidone ( PVP K‐30): A Temperature‐Dependent Dielectric Spectroscopy Study

The dielectric properties of polyvinylpyrrolidone (PVP K‐30) (C 6 H 9 NO) n in water have been investigated at different PVP concentrations across a frequency range of 0.01–30 GHz and a temperature region of 298.15–278.15 K using the time domain reflectometry (TDR) method. The obtained dielectric spectra show two relaxation peaks. Low‐frequency relaxation is due to the micro‐Brownian motion of the PVP main chain, which remains partially solvated and influenced by solute‐solvent interactions, whereas high‐frequency relaxation is caused by reorientation of bulk‐like water molecules. Using the Cole–Davidson model, the dielectric permittivity spectra were explained. When PVP molecules are present, the dynamical and structural properties of water have been examined using various dielectric and thermodynamic parameters. The dielectric parameters ( ε j , τ j , μ eff , g 1 , Z ib , and V eff ) and thermodynamic activation parameters (Δ F j , Δ S j , and Δ H j ) were systematically characterized. The results provide molecular‐level information of aqueous PVP systems under dilute and low‐temperature conditions. As PVP concentration increases, the static dielectric constant ( ε 1 ) of low‐frequency process rises, while the dielectric constant ( ε 2 ) of high‐frequency process decreases. As the temperature decreases and PVP concentration increases, the relaxation time for both relaxation processes ( τ 1 and τ 2 ) increases.