Molecular weight determination of acrylonitrile polymers by gel permeation chromatography in N,N‐dimethylformamide

Peculiar elution behavior of the GPC of acrylonitrile polymers was investigated. The peculiarity was considered to be due to some substances which form a supermolecular structure with acrylonitrile polymers to cause a large UV absorption, detectable at 280 nm. The Mark‐Houwink‐Sakurada parameters of acrylonitrile polymers in 0.01M LiBr‐DMF at 60°C, needed for GPC universal calibration, were determined to be K=2.12 × 10−4 and a=0.75. The parameters obtained by us were different from the ones by other investigators, however, these values were reasonable for random coil polymers. The addition of inorganic salt, such as LiBr, in DMF removed the peculiar elution behavior of the GPC. The universal calibration using monodisperse poly(ethylene oxide) standards and the Mark‐Houwink‐Sakurada parameters could be applied for the determination of the molecular weights. The invalidity of the universal calibration for acrylonitrile polymers in DMF containing LiBr, seems to be caused by the difficulty in the determination of the molecular weight of polyacrylonitrile standards by absolute methods, such as light scattering and osmometry.