POLYSOLVAT 16 at JCNS, Workshop 2026

Aqueous suspension of non-ionic poly(N-isopropylacrylamide) (PNIPAM) microgel particles was synthesized via free-radical precipitation polymerization. On the synthesized PNIPAM microgel particles, a dynamic light scattering experiment was performed, and hydrodynamic radii were determined to be roughly 240 and 125 nm for temperatures of 25C and 40C, respectively [1,2,3]. Dielectric relaxation studies were carried out on a 10wt.% PNIPAM solution prepared in a mixed solvent system of 70% water and 30% methanol, and on the pure solvent mixture, over a broad frequency range of 100 MHz to 50 GHz and at temperatures between 5C to 50C. The dielectric spectra for the pure water-methanol mixture showed a dominant relaxation process associated with the collective reorientation of hydrogen-bonded networks. The relaxation for the polymer solution arises from (i) polymer-solvent coupling and (ii) the restricted dynamics of water molecules confined within the polymer network. Upon increasing the temperature, both samples show decreased relaxation times, implying faster molecular reorientation and a gradual weakening of hydrogen-bond interactions [3]. As the temperature increases, both ε′ and ε″ decrease, indicating reduced dipolar polarization and dielectric loss due. The relaxation peak in ε″ shifts toward higher frequencies with increasing temperature. The findings of this study will be presented.

1. B Vijayakumar et al., Macromolecules, 55, 1218–1229 (2022).
2. B Vijayakumar et al., Physical Chemistry Chemical Physics, 25, 22223-22231(2023).
3. B Vijayakumar et al., Transactions on Dielectrics and Electrical Insulation, 30, 1657-1662 (2023).