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Effect of salt and surfactant concentration on the structure of polyacrylate gel/sutrfactant complexes

P. Nilsson ; Johan Unga (Institutionen för kemi- och bioteknik) ; P. Hansson
Journal of Physical Chemistry B (1520-6106). Vol. 111 (2007), 37, p. 10959-10964.
[Artikel, refereegranskad vetenskaplig]

Small-angle X-ray scattering was used to elucidate the structure of crosslinked polyacrylate gel/ dodecyltrimethylammonium bromide complexes equilibrated in solutions of varying concentrations of surfactant and sodium bromide (NaBr). Samples were swollen with no ordering (micelle free), or they were collapsed with either several distinct peaks (cubic Pm3n) or one broad correlation peak (disordered micellar). The main factor determining the structure of the collapsed complexes was found to be the NaBr concentration, with the cubic structure existing up to similar to 150 mM NaBr and above which only the disordered micellar structure was found. Increasing the salt concentration decreases the polyion mediated attractive forces holding the micelles together causing swelling of the gel. At sufficiently high salt concentration the micelle-micelle distance in the gel becomes too large for the cubic structure to be retained, and it melts into a disordered micellar structure. As most samples were above the critical micelle concentration, the bulk of the surfactant was in the form of miscelles in the solution and the surfactant concentration thereby had only a minor influence on the structure. However, in the region around 150 mM Nal3r, increasing the surfactant concentration, at constant NaBr concentration, was found to change the structure from disordered micellar to ordered cubic and back to disordered again.

Nyckelord: OPPOSITELY CHARGED SURFACTANT, CUBIC PHASE I1, POLYELECTROLYTE GEL, IONIC SURFACTANTS, DODECYL-SULFATE, MICROGELS, BEHAVIOR, DENSITY, MIXTURES, KINETICS



Denna post skapades 2008-12-10.
CPL Pubid: 80921

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik (2005-2014)

Ämnesområden

Kemiteknik

Chalmers infrastruktur