| Abstract: | Abstract The calibration of gel permeation chromatograph (GPC) for a given polymer type is usually done by running well-characterized polymer samples of the same type. The available polystyrene and polyglycol standards with molecular weights below 5000 do not give parallel calibration curves, and the points for polystyrene are not on an extension of the higher-molecular-weight portion of the curve. In order to check the calibration in this low molecular-weight region and to establish an independent curve for polybutadiene, a polybutadiene sample prepared by a-methylstyrene tetramer-Na2 initiation was chromatographed. In doing this, dual detection was used, consisting of a differential refractometer, and an ultraviolet absorption spectrophotometer. The UV signal from the spectrophotometer was assumed to represent the tetramer portion of the polymer, and its percentage was calculated at each volume increment, using externally determined response factors. This percentage and the tetramer molecular weight gives the molecular weight of the polymer eluting at each volume increment. After correction for the aromatic portion of the polymer, these data and the points obtained with the polybutadiene standards were found to give a reasonable calibration curve for the entire range. The present paper describes the application of this technique to the examination of low molecular-weight polybutadiene. |
