https://doi.org/10.1140/epje/i2014-14063-8
Regular Article
Study on enthalpy relaxation of glassy polystyrene using a structure-dependent Kohlrausch stretch exponent combined with coupling model
Institute of Polymer Science and Engineering, Hebei University of Technology, 300130, Tianjin, China
* e-mail: liugd@hebut.edu.cn
Received:
23
December
2013
Revised:
24
March
2014
Accepted:
17
June
2014
Published online:
24
July
2014
In this paper the enthalpy relaxation of polystyrene (PS) was restudied using a structure-dependent Kohlrausch stretch exponent β with incorporation of a coupling model (CM). The structure dependence of β is described in 3 semi-phenomenological equations. The temperature and structure dependence of the relaxation time of the Johari-Goldstein (JG) relaxation (τ JG) is presented using the traditional Tools-Narayanaswamy-Moynihan (TNM) and Adam-Gibbs-Vogel (AGV) equations. The fitting results of heat capacity data are much better than the conventional TNM and Adam-Gibbs (AG) models when the structure dependence of β is described using an exponential equation and τ JG is calculated using the AGV equation, although there are one fewer fitting parameters in the new model. The results indicate that both the structure dependence of β and the CM model may play considerable roles in the investigation on the structure relaxation process in polymers around the glass transition.
Key words: Soft Matter: Polymers and Polyelectrolytes
© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg, 2014