Polymer Engineering and Science, Vol.39, No.8, 1383-1388, 1999
Precipitation-redissolution liquid chromatography of styrene-ethyl acrylate copolymers
The technique of Precipitation-Redissolution Liquid Chromatography (PRLC) has been applied for fractionation of styrene-ethyl acrylate copolymers in the whole composition range, from one homopolymer to the other. Two different polar types of column packings were used, pure silica and CN modified silica. Samples dissolved in tetrahydrofuran were injected in the columns where a nonsolvent mixture is used as chromatographic mobile phase. Polymers precipitate in the columns, and their elution is obtained by applying a gradient of eluent with increasing polarity and solvent power. The different copolymers, and the homopolymers, could be separated as a function of acrylate unit content. The best gradient conditions were obtained with a compromise between resolution, efficiency and analysis time. It was found that the polarity of the packing influences the separation in term of retention and peak resolution. This means that a composite mechanism is involved, with adsorption effects adding to the precipitation in favoring the fractionation according to the sample polarity.