Molecular dynamics of poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogels studied by broadband dielectric spectroscopy

Rheological and dielectric behavior of sodium carboxymethyl cellulose (NaCMC)/Ca2+ and esterified NaCMC/Ca2+ hydrogels: Correlating microstructure and dynamics with properties

Polyelectrolyte-based conductive hydrogels are being extensively explored for applications in energy storage and as electrode materials for batteries. We synthesized ionically crosslinked sodium carboxymethyl cellulose (NaCMC), esterified NaCMC, and Ca2+ doped esterified NaCMC hydrogels. This work aims to understand the effect of Ca2+ ions on the NaCMC and esterified NaCMC. FTIR, SEM, Rheology and EIS studies were performed to understand the structure and dynamics of hydrogels. Results confirmed that Ca2+ ions have an important role in determining the rheological and dielectric response of hydrogels. Power law behavior was observed in their rheological response with exponent (n) of 0.81 for G' and 0.76 for G″ of ionically crosslinked NaCMC, 5.38 for G' and 4.70 for G″ of esterified NaCMC, whereas, negative exponents -1.44 for G' and -1.10 for G″ of Ca2+ ion doped esterified NaCMC. Ionically crosslinked NaCMC hydrogels have relaxation times (τ) in the range of 8.9 × 10-5 s-2.8 × 10-5 s may be due to the formation of temporary dipoles by electrostatic bridge formations with dc conductivity of (0.1 S/cm-5 S/cm), whereas, esterified NaCMC showed relaxation times (10-3 s-8.9 × 10-5 s) with increasing ester crosslinks and dc conductivity of (0.05 S/cm-0.8 S/cm). Interestingly, Ca2+ ion doped esterified hydrogels showed multiple dielectric relaxations on Ca2+ ion addition with different relaxation times may be due to change in ionic environment. The understanding obtained from this work may be useful for designing tuneable hydrogels with optimum electrical and mechanical properties.

An Overview on Recent Progress of the Hydrogels: From Material Resources, Properties to Functional Applications

Hydrogels, as the most typical elastomer materials with three-dimensional network structures, have attracted wide attention owing to their outstanding features in fields of sensitive stimulus response, low surface friction coefficient, good flexibility and bio-compatibility. Because of numerous fresh polymer materials (or polymerization monomers), hydrogels with various structure diversities and excellent properties are emerging, and the development of hydrogels is very vigorous over the past decade. This review focuses on state-of-the-art advances, systematically reviews the recent progress on construction of novel hydrogels utilized several kinds of typical polymerization monomers, and explores the main chemical and physical cross-linking methods to develop the diversity of hydrogels. Following the aspects mentioned above, the classification and emerging applications of hydrogels, such as pH response, ionic response, electrical response, thermal response, biomolecular response, and gas response, are extensively summarized. Finally, we have done this review with the promises and challenges for the future evolution of hydrogels and their biological applications. cross-linking methods; functional applications; hydrogels; material resources This article is protected by copyright. All rights reserved.