Reconcentration of diluted polymer solutions by full adsorption/desorption procedure: II. Desorption of macromolecules by a narrow pulse of displacer

Abstract

Diluted polymer solutions can be effectively reconcentrated applying full adsorption/desorption processes. Macromolecules from diluted solutions are quantitatively retained within a bed of appropriate adsorbent. Next, the polymer is released by a high-strength desorbing liquid that is introduced into the sorbent bed as a narrow pulse. To evaluate the above reconcentration procedure, medium-polarity polymers, mainly poly(methyl methacrylate)s of various molar mass distributions were chosen as model species. Nonporous silica was used as an adsorbent, toluene and chloroform as adsorbing liquids, and tetrahydrofuran as a desorbing liquid in an HPLC-like apparatus. The concentration profiles of both the desorbing liquid pulse and desorbed polymer were monitored with the usual LC detectors. On-line size exclusion chromatography was employed in selected cases to determine molar mass and molar mass distribution of desorbed macromolecules. The effect of some experimental parameters on the reconcentration efficiency was elucidated, viz. the nature of the sample solvent-adsorbing liquid, flow rate of desorbing liquid, molar mass, molar mass distribution, and nature of reconcentrated polymer, as well as relations among the amount of the polymer to be reconcentrated and the volume of the desorbing liquid pulse. It is shown that very high reconcentration factors can be readily obtained by the full adsorption–desorption procedure if the experimental conditions are carefully optimized. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 267–275, 1999