On the molecular weight dependence of the thermodynamic and of the hydrodynamic pair interaction between chain molecules. IV. Second virial coefficients revisited

摘要

In the preceding papers of this series, it has been shown theoretically and experimentally how the Floryndash;Huggins interaction parameter khgr; and the Huggins coefficientkHfor polymers differing in molecular weight are built up from the contributions of interhyphen; and intramolecular contacts between polymer segments. In the present work, new experimental material concerning solutions of wellhyphen;fractionated polyisobutene (PIB) and polystyrene (PS) is presented which, for the first time, includes worse than theta conditions. Its evaluation corroborates the above concept and reveals two features not observed so far. As the solvent quality becomes very unfavorable, the parameters measuring theintermolecular contacts between segments increase as one would expect from the data obtained for good solvent conditions. In contrast to that, theintramolecular parameters no longer decrease smoothly below theta conditions, but show a drastic reduction. This behavior is attributed to coilhyphen;collapse phenomena. The second feature concerns the following observation: If the interhyphen; and intramolecular parameters are plotted as a function of the Kuhnndash;Markndash;Houwink exponent, differences in the behavior of PIB and PS become noticeable under certain conditions. These observations are explained by the influence of the particular architecture of the polymer chain.