Dynamic Behaviors of Solvent Molecules Restricted in Poly (Acryl Amide) Gels Analyzed by Dielectric and Diffusion NMR Spectroscopy.

Hironobu Saito,Minoru Fukuzaki,Keisuke Matsumoto,Naoki Shinyashiki,Rio Kita,Masayuki Tokita,Yuya Umino,Shunpei Kato,Shin Yagihara

doi:10.3390/gels4030056

Hironobu Saito, Minoru Fukuzaki + Show 7 more

Open Access

https://doi.org/10.3390/gels4030056

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Journal: Gels	Publication Date: Jun 22, 2018
Citations: 8	License type: CC BY 4.0

Affiliation: Tokai University, Kyushu Tokai University, Kyushu University

Abstract

Dynamics of solvent molecules restricted in poly (acryl amide) gels immersed in solvent mixtures of acetone–, 1,4-dioxane–, and dimethyl sulfoxide–water were analyzed by the time domain reflectometry method of dielectric spectroscopy and the pulse field gradient method of nuclear magnetic resonance. Restrictions of dynamic behaviors of solvent molecules were evaluated from relaxation parameters such as the relaxation time, its distribution parameter, and the relaxation strength obtained by dielectric measurements, and similar behaviors with polymer concentration dependences for the solutions were obtained except for the high polymer concentration in collapsed gels. Scaling analyses for the relaxation time and diffusion coefficient respectively normalized by those for bulk solvent suggested that the scaling exponent determined from the scaling variable defined as a ratio of the size of solvent molecule to mesh size of polymer networks were three and unity, respectively, except for collapsed gels. The difference in these components reflects characteristic molecular interactions in the rotational and translational diffusions, and offered a physical picture of the restriction of solvent dynamics. A universal treatment of slow dynamics due to the restriction from polymer chains suggests a new methodology of characterization of water structures.

Highlights

Polymer gels, i.e., crosslinked polymer networks with solvent have been extensively applied in diverse fields such as medical, environment, and food science and industries because of the characteristic behaviors
One of the authors (M.T.) has reported that diffusion coefficients of probe molecules obtained by the pulsed field gradient spin echo method of nuclear magnetic resonance (PFG-Nuclear magnetic resonance (NMR)) [7,8]
We have investigated the dynamic behavior of solvent molecules restricted in polymer networks of gels [14,15] by using the time domain reflectometry (TDR) method [16,17,18] of microwave dielectric spectroscopy

Summary

Introduction

I.e., crosslinked polymer networks with solvent have been extensively applied in diverse fields such as medical, environment, and food science and industries because of the characteristic behaviors. One of the most typical and characteristic behaviors of polymer gels is a volume phase transition with which the late Professor Tanaka has first indicated that fundamental physics of polymer gels, leading to expanded usage in applied science. Gels 2018, 4, 56 physical properties of the polymer gel related to the volume phase transition, especially from a view point of molecular interactions among the solvent molecules and polymer chains. Showed dynamic behaviors of probe molecules restricted in polymer gels [9,10,11]. The mesh size of the network could be evaluated from the restriction of various probe molecules with different sizes

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Conclusion