Concentration Dependence of Elution Volumes in size Exclusion Chromatography of Polymer Molecules. II. Poly(Methyl Methacrylate) in Ideal Solvent

Abstract

The concentration effects occurring in size exclusion chromatography of polymer molecules have been investigated for the case of elution of macromolecules in an ideal solvent. It is shown that increases in the elution volumes with polymer concentration are detectable with the high efficiency columns employed. The concentration dependence of elution volumes is much lower than that previously determined with good solvents. The main factor contributing to the shift of elution volumes seems to be the viscosity of the polymer solutions, but another effect appears also to be present. This latter effect possibly suggest that in semi-concentrated solutions of polymer molecules in ideal solvents a continuous contraction of the polymer chains occurs, below their unperturbed dimensions, similar to that happening when the temperature of ideal solutions is decreased. More investigation on this point is needed. the ideal solutions is increased. Further investigations will be carried out to clarify this point.

In conclusion, the concentration dependence of polymer elution volumes in SEC has been found to be detectable also in a thermodynamically ideal solvent, though it is much lower than that observed in good solvents. In such a system, the main cause of the shift of elution volumes appears to be the viscosity of the polymer solutions, but a small additional contribution is also seen to be present. At the moment, it seems not possible to evaluate with certainty the origin of this latter contribution, especially in the absence of data on the macromolecular conformations in semi-concentrated solutions in ideal solvents.