Phenomenological theory of structural relaxation based on a thermorheologically complex relaxation time distribution

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• 作者：L. Andreozzi ; M. Faetti ; M. Salmerón Sanchez and J. L. Gómez Ribelles
• 关键词：PACS 64.70.pj Polymers ; 64.70.kj Glasses ; 64.70.km Polymers ; 61.43.Fs Glasses
• 刊名：The European Physical Journal E - Soft Matter
• 出版年：2008
• 出版时间：September, 2008
• 年：2008
• 卷：27
• 期：1
• 页码：87-97
• 全文大小：300.1 KB
• 刊物类别：Physics and Astronomy
• 刊物主题：Physics
  Soft Matter and Complex Fluids
  Biotechnology
  Physical Chemistry
  Polymer Sciences
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1292-895X

文摘

The aim of this work is to explore the consequences on the kinetics of structural relaxation of considering a glass-forming system to consist of a series of small but macroscopic relaxing regions that evolve independently from each other towards equilibrium in the glassy state. The result of this assumption is a thermorheologically complex model. In this approach each relaxing zone has been assumed to follow the Scherer-Hodge model for structural relaxation (with the small modification of taking a linear dependence of configurational heat capacity with temperature). The model thus developed contains four fitting parameters. A least-squares search routine has been used to find the set of model parameters that fit simultaneously four DSC thermograms in PVAc after different thermal histories. The computersimulated curves are compared with those obtained with Scherer-Hodge model and the model proposed by Gómez and Monleón. The evolution of the relaxation times during cooling or heating scans and also during isothermal annealing below the glass transition has been analysed. It has been shown that the relaxation times distribution narrows in the glassy state with respect to equilibrium. Isothermal annealing causes this distribution to broaden during the process to finally attain in equilibrium the shape defined at temperatures above T _g .