SIMULATION OF POLYMER-CHAIN DYNAMICS WITH SMALL ORGANIC-MOLECULES AND THEIR MIXTURES

Experimental simulation of polymer properties or structure with small organic molecules is a well-known technique that appears not to have been applied to the study of polymer chain dynamics. In this work we apply this simulation methodology by examining the dielectric relaxation data on isoamyl bromide and its mixtures with 2-methylpentane reported by Denney et al. These molecules form an interesting pair for study because they are isometric, they form solutions over their entire composition range, and one of them is a simple polar molecule while the other is nonpolar. They also tend to form glasses rather than crystallize when cooled to low temperatures. Denney's relaxation data are represented in terms of a function proposed by Havriliak and Negami for polymers. The parameters of this function as well as their dependence on temperature were determined by using the multiresponse techniques developed by Havriliak and Watts. The dynamic parameters for the mixtures in the 50-75 mol % range of isoamyl bromide are similar to the parameters for the α-relaxation process of many polymers previously reported. The parameters are discussed in terms of the general Kirkwood-Cole theory of polar liquid relaxation and Mansfield's specific model for polymer chain dynamics. The experimental results described in this work support the results derived from Mansfield's model for polymer chain dynamics, i.e., the shape of the dielectric relaxation process when viewed in a complex plane is not due to molecular weight but is due to the nature and relative magnitudes of the intramolecular and intermolecular interactions. © 1990 American Chemical Society.