Gel chromatographic fractionation of styrene oligomers

A series of styrene oligomers having propyl end groups was prepared by oligomerization of styrene with ethyllithium followed by termination with l‐bromopropane. The fractionation of the oligomers by molecular weight and into diastereomers was investigated by gel chromatography using a high resolution styrene‐divinylbenzene gel. The most suitable eluents for the fractionation were chosen by the study of the elution behavior of the oligomers using various eluents having different polarity. The fractionation by molecular weight was done with chloroform as eluent and the 2‐ to 11‐mers of styrene were collected with purities higher than 95%. The isolated 2‐ to 5‐mers were further separated into diastereomers using diisopropyl ether as an eluent. The dimer and the trimer were fractionated into pure diastereomers. The tetramer was separated into 6 diastereomers and the fractionation of the pentamer was also relatively successful.