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Concentration Effect on Temperature Dependence of Gelation Rate in Aqueous Solutions of Methylcellulose
Author(s) -
Chen Kai,
Baker Ashley N.,
Vyazovkin Sergey
Publication year - 2009
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200800518
Subject(s) - activation energy , nucleation , thermodynamics , chemistry , diffusion , kinetics , aqueous solution , power law , polymer chemistry , physics , mathematics , statistics , quantum mechanics
The gelation kinetics in methylcellulose solutions of different concentrations is studied by DSC under rising temperature conditions. Isoconversional analysis reveals that the rate is a complex function of temperature represented by a concave downward dependence of the effective activation energy on temperature ( E vs. T ). Although the initial decreasing portion of the dependence is consistent with the Fisher–Turnbull nucleation model, a description of the final increasing part requires introducing activation energy of diffusion that varies with conversion according to a power law. Parameters of the modified model evaluated from the E versus T dependencies suggest that the diffusion contribution increases with increase in the concentration, whereas the free energy barrier to nucleation remains almost unaffected.