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<p>The poly(methacrylic acid) (PMAA) hydrogel is synthesized, and non-isothermal thermogravimetric curves of PMAA hydrogel dehydration are recorded at four heating rates in the interval from 5 to 20 K min<sup>−1</sup>. The dependence of apparent activation energy on the dehydration degree is determined by Vyazovkin’s isoconversional method. Commonly used kinetic models for nucleation-controlled processes were applied to fit the experimental conversion curves, with the Gompertz function providing an excellent fit across all heating rates. The dependencies of model equation parameters (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(a\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>a</mi> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(b\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>b</mi> </math></EquationSource> </InlineEquation>) on heating rate, as well as the rate constant on temperature and kinetics parameters on both temperature and dehydration degree, are determined. Regardless of the heating rate, thenon-isothermal dehydration of PMAA hydrogel can be effectively described by a single activation energy distribution function. The experimental findings are supported by quantum chemistry calculations. The results suggest that the state of absorbed water evolves continuously during dehydration, with each change in water content driving ongoing structural rearrangements in the hydrogel and a corresponding continuous shift in the energy state of the absorbed water.</p>

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The kinetics analyses of non-isothermal dehydration of poly(methacrylic acid) hydrogel by application of nucleation model

  • 期刊论文

  • 发表日期：

    2026年3月6日

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  • Branislav Stanković

摘要

The poly(methacrylic acid) (PMAA) hydrogel is synthesized, and non-isothermal thermogravimetric curves of PMAA hydrogel dehydration are recorded at four heating rates in the interval from 5 to 20 K min−1. The dependence of apparent activation energy on the dehydration degree is determined by Vyazovkin’s isoconversional method. Commonly used kinetic models for nucleation-controlled processes were applied to fit the experimental conversion curves, with the Gompertz function providing an excellent fit across all heating rates. The dependencies of model equation parameters ( \(a\) a and \(b\) b ) on heating rate, as well as the rate constant on temperature and kinetics parameters on both temperature and dehydration degree, are determined. Regardless of the heating rate, thenon-isothermal dehydration of PMAA hydrogel can be effectively described by a single activation energy distribution function. The experimental findings are supported by quantum chemistry calculations. The results suggest that the state of absorbed water evolves continuously during dehydration, with each change in water content driving ongoing structural rearrangements in the hydrogel and a corresponding continuous shift in the energy state of the absorbed water.