Examination of polymer size parameters for universal calibration in gel permeation chromatography

Abstract

Various procedures for universal calibration in gel permeation chromatography with polystyrene gels are examined for polystyrene and poly(dimethylsiloxane) fractions. For o-dichlorobenzene at 138°, experimental intrinsic viscosity-molecular weight data show that the Mark-Houwink exponents are 0.70 and 0.57 for polystyrene and poly(dimethylsiloxane), respectively. In principle, this difference permits a distinction between the various polymer size parameters proposed for universal calibration. An interpretation of the experimental poly(dimethylsiloxane) calibration for o-dichlorobenzene at 138° requires a consideration of errors in average molecular weights and errors arising from the use of average molecular weight instead of peak molecular weight. When hydrodynamic volume and unperturbed dimensions calibration procedures are examined, the difference between them is comparable with experimental error. If the F lory-F ox viscosity expression is employed, the perturbed end-to-end distance (or radius of gyration) gives an equivalent universal calibration to the hydrodynamic volume. The experimental data are sufficiently accurate to show that the perturbed dimension determined with the P titsyn-E izner relation does not give an adequate universal calibration.