ABSTRACT:The models of Yamakawa and Rudin were used to predict the effects of polymer concentration on hydrodynamic volumes of solvated macromolecules and on peak elution volumes in gel-permeation chromatographic (GPC) analyses. Both theories predict GPC behavior accurately for all systems of practical analytical interest. Yamakawa theory calculations predict that a concentration region may exist in which the polymer hydrodynamic volume may be greater in a poorer solvent than in a thermodynamically better solvent. This "cross-over" is noticeable for high molecular weight polymers at relatively high concentrations which are beyond the dilute region for which the theory was developed. Some GPC observations with porous glass packings are nevertheless in qualitative agreement with this prediction. Both models account for the effects of concentration, solvent choice, and polymer molecular weight on GPC column behavior.KEY WORDS Hydrodynamic Volume I Elution Volume I GPC I Gyration Radius I It is well known that the peak elution volume tends to increase with increasing concentration of a given polymer in the feed to GPC column sets. 1 -10 The concentration effect is more pronounced with polymers of narrow molecular weight distribution and higher mean molecular weight. The effect of concentration decreases as the thermodynamic quality of the GPC solvent deteriorates and is practically non-existent in theta mixtures.The concentration effect in GPC was explained as a consequence of the reduction of the effective hydrodynamic volume of solvated polymer coils with increasing concentration. A semi-empirical model has been discussed which can be used to correct for concentration effects in GPC. 11 This model has also been applied to universal calibration in GPC. 12 The theory did not fit experimental observations in theta solvents and a revision (herein-after referred to as the Rudin model) has been published which is less empirical and which appears to fit the elution behavior of polymers in all * On leave from Chemical Engineering Department, Arya-Mehr University of Technology, Tehran, Iran. GPC solvents. 9 ' 13 -16 The Rudin model seems to be the only one which has been used quantitatively to correct GPC data for concentration effects. It was of interest, therefore, to determine whether a model which is accepted as more "orthodox" in current polymer solution theory would also be applicable to this practical problem. In this article, we compare the Rudin model 13 with Yamakawa's 17 theory relating the concentration and effective hydrodynamic volume of solvated polymers. It will be shown that the two theories yield equivalent predictions under almost all conditions which are likely to be encountered in GPC analyses. The two deviate only in the case of very high molecular weight polymers at relatively high concentrations in very good solvents. The Rudin model is more convenient to use. The Yamakawa theory predicts that the dimensions of a high molecular weight polymer coil in a good solvent may be smaller than those in a...