Novel methods for the characterization of water-soluble polymers

✍ Scribed by Artur Bartkowiak; David Hunkeler; Dusan Berek; Tadeusz Spychaj

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 222 KB
• Volume: 69
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19980926)69:13<2549::aid-app4>3.0.co;2-a

✦ Synopsis

The liquid chromatography of four water-soluble polymers [pullulan, polyacrylamide, poly(ethylene glycol), and poly(ethylene oxide)] have been investigated and used to categorize separation processes which couple enthalpic and entropic mechanisms. Experiments were carried out with a binary mobile phase which combined a thermodynamically good solvent (water or aqueous 0.02 M Na 2 SO 4 ) and nonsolvent (methanol). The polymer solute was injected in a good solvent. By varying the solventnonsolvent ratio in the eluent, conditions could be obtained where the free energies of exclusion and solvation were balanced. This has been given the nomenclature ''liquid chromatography under limiting conditions of solubility'' (LC-LCS) since the polymer elutes just in front of the system peak at the ''limit'' of its solubility. Conditions can also be identified where exclusion is balanced with adsorption (''liquid chromatography under limiting conditions of adsorption,'' or LC-LCA). To our knowledge, these are the first experimental reports of LC-LCS for any polymer and the first LC-LCA observation on water-soluble macromolecules. All measurements were carried out over a poly(hydroxymethylacrylate) sorbent. Cloud point curves were found to generally distinguish the regions where LC-LCA or LC-LCS dominate. The data illustrate the need to consider the polymer when analyzing LC-LCA. Conversely, polymer adsorption may play an important role in LC-LCS.