Fractionation of polymers by precipitation chromatography—microtechnique and theory

A microcolumn for fractionation by precipitation chromatography is described. It operates in conjunction with a continuous paper‐strip fraction collector, and has been used successfully to fractionate milligram quantities of polysarcosine dimethylamide. Polymer which can either be labelled or dyed may be determined directly on the strip by scanning methods. A semi‐empirical theoretical consideration of the column has resulted in the followimg molecular weight vs. volume relationship (for the case of a single constant volume solvent‐precipitant mixing chamber): where T 2 is the temperature at the, bottom of the column, G is the volume of the mixing chamber, and τ and (σ+τ) may be identified with the Flory temperatures of solvent and precipitant, respectively. This has been found to be a close fit to published data for the fractionation of polystyrene. A comparison of exponential and constant solvent gradients shows that the former are advantageous for very broad distributions, the latter for narrow.