Effective Dimensions of Oligomers in Size Exclusion Chromatography. A Molecular Dynamics Simulation Study

Size exclusion chromatography (SEC) is a widely used method for determining the molecular weights of polymer molecules. SEC calibration is often achieved using the “universal calibration” technique, which assumes hydrodynamic volume is the sole determinate of retention time. Recent work has demonstrated the failure of this approach when molecular weights are small ( PIB > PE. This order agrees with experimental SEC data for retention times for these oligomer series. The differences are attributed to asphericity of individual configurations enhancing the effects of substituent size. The approach of the mean-square radius of gyration and mean-square end-to-end distance dependence on chain length to limiting long-chain behavior is discussed. It is found that the limiting proportionality to chain length has not been reached in the molecular weight ranges studied. A comparison of the use of the intrinsic viscosity−molecular weight product ([η]M) as a measure of radius of gyration, the radius of gyr