Dynamic Surface Tension of Aqueous Polymer Solutions, I: Ethyl(hydroxyethyl)cellulose (BERMOCOLL cst-103)

✍ Scribed by Inger Nahringbauer

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 209 KB
• Volume: 176
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1995.9961

✦ Synopsis

The dynamic surface tension of aqueous solutions of ethyl(hythe bulk to the water surface is a complete explanation of droxyethyl)cellulose (EHEC) was measured using the pendantthe time variation or whether some additional effect must drop method and digital-image analysis. The EHEC concentrabe sought (11)(12)(13)(14); tions studied ranged from 3.2r10 05 to 0.28% w/w. The time -to discuss the origin of the enhanced rate of surfacedependence of surface tension was analyzed using a diffusiontension decrease, whether or not the polymer chains are kinetics-controlled theory where the adsorption kinetics depended extended at the surface due to reconfiguration (12); and on the fraction of the total surface coverage. For EHEC concentra--to investigate the experimental conditions under which tions £10 03 % w/w, the isotherms showing surface tension vs log the adsorption processes lead to a film (reversible or irreverstime follow a sigmoidal pattern. Three consecutive kinetic regions exist: the induction region, the surface-coverage region, and the ible) (13). mesophase region. The process of the adsorption of polymer seg-Fundamental properties of polymer molecules, such as ments is described in terms of relaxation times and the critical molecular weight and flexibility, make macromolecular adpoints of time, at the onset and at the end of the region of surface sorption different from adsorption of substances of low mocoverage. An extremely slow surface equilibration in the mesolecular weight. This applies especially to the surface activity phase region indicates a progressive ordering of the polymer segand conformation of the adsorbed molecule. Polymer molements within the surface layer.