A comparative study of the viscosity of ion conducting polymers based on the bond strength-coordination number fluctuation model and other models

Abstract

According to the bond strength-coordination number fluctuation (BSCNF) model of viscosity proposed some years ago by one of the authors, viscosity is controlled by the relaxation of structural units that form the melt, and is described in terms of the average bond strength, coordination number, and their fluctuations of the structural units. In the present paper, a comparative study of the viscosity of ion conducting polymeric system is presented. The analysis has been done though the BSCNF model and other models widely used in the literature such as Vogel-Fulcher-Tamman and Williams-Landel-Ferry equations. The result reveals that the three models describe well the temperature dependence of the viscosity reported experimentally. As a gross trend, the fragility of the polymeric system in consideration increases with the increase in the concentration of salts. Based on the analysis with the BSCNF model, such a behavior has been interpreted to arise from the disruption of the network that results by the addition of salts. The comparative study also reveals that the BSCNF model could provide a physical interpretation to the empirical parameters used in other models.

Network Relaxation and Cooperativity in Ion Conducting Polymers PEO-Li: An Analysis Based on the BSCNF Model

“…[12]. From the figure we recognize that strong systems such as SiO2 are well characterized by small value of B and large value of C. On the other hand, fragile systems such as ZBLA (a fluoride compound) are characterized by an opposite trend of the parameters, i.e., large value of B and small value of C. The BSCNF model applied to polymers and ionic liquids[13][14][15] indicated that these materials are placed in an area of the B-C mapping characterized by large values of B and small values of C compared to other type of materials as illustrated by the parabolic region shown in Fig.1. That is, the mapping indicates that in polymer and ionic liquids, the bond strength between the constituent elements (monomers in the case of polymers) is small and its fluctuation is large.…”

“…Characterization of different materials in the B-C mapping[12]. The typical values of B and C for polymers and ionic liquids[13][14][15] are found in the marked region. The dotted curves show the behavior described by the BSCNF model.…”