The dimensionless parameter, A ~.Mw/[r~], has been obtained from measurements on amylose acetate fractions in nitromethane. These experimental results have been compared with various theoretical treatments. It has been shown that the semi-empirical equation of Krigbaum gives the best description of the experimental values. Furthermore, application of this theory gives a value for the unperturbed dimensions of amylose acetate in excellent agreement with those obtained from lightscattering and sedimentation measurements.
THEORIES developed to account for the values of the second virial coefficient, A 2, of dilute polymer solutions are many in number, because of the different approximations introduced to deal with (a) interchain interactions, (b) intrachain interactions, and (c) the combination of (a) and (b). In this paper, we review these theories and apply them to the system of amylose acetate in nitromethane.
EXPERIMENTAL AND RESULTS
Linear amylose was isolated from potato starch and was subfractionated from dimethyl sulphoxide solution by the addition of butanol. The preparation of the acetate, and the physical measurements carried out on the fractions have been detailed elsewhere.(1. 2~