Universal calibration procedures in gel permeation chromatography. Examination of poly(dimethyl siloxane) in a theta solvent

Abstract

AbstractGel permeation chromatography calibrations for polystyrene standards and poly‐(dimethyl siloxane) fractions have been obtained with polystyrene gel using o‐dichlorobenzene at 87°C. Intrinsic viscosity‐molecular weight data show that, at this temperature, o‐dichlorobenzene is a theta solvent for poly(dimethyl siloxane) but a good solvent for polystyrene. The KUHN‐MARK‐HOUWINK exponents are 0.50 and 0.73 for poly(dimethyl siloxane) and polystyrene respectively. This significant difference in polymer/solvent interaction allows assessment of various universal calibration procedures. Comparison of the experimental poly(dimethyl siloxane) data with curves calculated from a polystyrene calibration suggests that the most suitable calibration procedures use the hydrodynamic volume or the perturbed dimensions given by the FLORY‐FOX equation. Calibration procedures based on the unperturbed dimensions or on the perturbed dimensions derived from the PTITSYN‐EIZNER equation are not valid when the difference in the KUHN‐MARK‐HOUWINK exponents is large. For experimental calibrations with fractions, the position of molecular weight and hydrodynamic volume calibrations may depend on the choice of average molecular weight. The influence of fraction polydispersity on the plots is discussed.