High Performance Gel Permeation Chromatography of Polymers

The determination of the molecular weight distribution by gel permeation chromatography requires the establishment of a molecular weight calibration and efficient columns in order to minimise chromatogram broadening. The separation process is described in terms of steric exclu— sion, retardation and partial exclusion mechanisms in order to show how the universal calibration method may be influenced by solute-gel interactions. Solute dispersion mechanisms are described to show how chromat— ogram broadening is determined by the particle size of the column packing, the eluent flow rate, and the solute diffusion coefficient. Consequently, extensive chromatogram broadening will occur for permeating high polymers at fast flow rates, the decrease in column efficiency with flow rate becoming more significant as solute size rises. Therefore, accurate mole— cular weight distributions may be determined by high performance gel permeation chromatography with microparticulate packings at low eluent flow rates. For small molecules efficient separations occur at fast flow rates, so that high speed and high resolution separations of prepolymers and low polymers may be performed by gel permeation chromatography.