Abstract
Dielectric relaxation of poly(N-isopropylacrylamide) (PNiPAM) was investigated in 1,4-dioxane as a low-polarity solvent at a concentration between 0 and 20 wt %, temperature between 40 and −35 °C, and a frequency range between 40 Hz and 1.8 GHz. Results suggest that relaxation due to the molecular motion of PNiPAM has two components: relaxation of side-group rotational motion at ∼100 MHz and micro-Brownian motion of PNiPAM chain at ∼1 MHz at room temperature. These processes are described by the sum of two Cole–Cole equations. Furthermore, the relaxation times of these processes showed distinct temperature dependences, as confirmed by activation energies obtained from the Arrhenius plot. In addition, asymmetric relaxation was observed in the MHz region of PNiPAM in various solvents comprising two individual relaxations. This could explain some fundamental aspects of PNiPAM solution properties and provide a deeper understanding of the molecular dynamics of PNiPAM.
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