HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF POLYMERS - RETENTION MECHANISMS AND RECENT ADVANCES

The high-resolution separation of polymer oligomers, their breakdown p roducts and isomers is a significant challenge to modern separation sc ience. The historically most successful methods are based on size excl usion strategies and not mobile phase/stationary phase partition in th e conventional sense. In the last decade significant progress has been made in understanding the requirements for achieving elution chromato graphy of high {> 5 kDa} molecular weight organic polymers ranging fro m quite hydrophobic to quantitatively water soluble in character. This paper discusses retention mechanisms, the dynamics of the partition c hromatographic process, evidence for significant delays in polymer equ ilibration to mobile phase conditions and the effect of the temperatur e dependence of polymer solubility. Conventional chromatographic behav ior is shown to obtain for the separation of polystyrenes, polymethylm ethacrylates, polyethylene oxides and polypeptides if proper steps are taken to carry out the experiment. The use of thermal gradients in sp atial terms is shown to have significant value for achieving enhanced separations.