SEPARATION OF STYRENE-ACRYLONITRILE COPOLYMERS BY STEPWISE GRADIENT ELUTION - HIGH-PERFORMANCE PRECIPITATION LIQUID-CHROMATOGRAPHY

With stepwise gradient elution of styrene-acrylonitrile copolymers with an ODS-silica column using chloroform - n-hexane mixtures as mobile phases, each copolymer was separated into six to eight peaks. The initial mobile phase was n-hexane and the content of chloroform in the mobile phase was increased 2% every five or ten minutes. Separated peaks were fractionated and the acrylonitrile (AN) content and molecular weight averages were measured. The copolymers were separated in order of increasing the AN content and molecular weight with few exceptions. This explains that the fractions having lower molecular weight have lower AN content.