Excluded-Volume Effects

Abstract

This chapter deals with the theory of the excluded-volume effects in dilute solution, such as various kinds of expansion factors and the second and third virial coefficients, developed on the basis of the perturbed HW chain which enables us to take account of both effects of excluded volume and chain stiffness. Necessarily, the derived theory is no longer the two-parameter (TP) theory [1], but it may give an explanation of experimental results [2] obtained in this field since the late 1970s, which all indicate that the TP theory breaks down. There are also some causes other than chain stiffness that lead to its breakdown. On the experimental side, it has for long been a difficult task to determine accurately the expansion factors since it is impossible to determine directly unperturbed chain dimensions in good solvents. However, this has proved possible by extending the measurement range to the oligomer region where the excluded-volume effect disappears. Thus an extensive comparison of the new non-TP theory with experiment is made mainly using such experimental data recently obtained for several flexible polymers. As for semiflexible polymers with small excluded volume, some remarks are made without a detailed analysis.