Viscometric study of the sodium hyaluronate-sodium chloride-alkyl-(n)-ammonium surfactant system

Viscosity and rheological properties of the system sodium hyaluronate (NaHA)-NaCl-alkyl-(n)-ammonium surfactant were studied. The system with monomeric (n=1) surfactant dodecyltrimethylammonium bromide DTAB separated into two phases below the 200 mM NaCl concentration. At high NaCl concentration (>0.3 M), the hyaluronate–surfactant interaction is screened. At low NaCl concentration (0.2 M), the hyaluronate–surfactant interaction appears at higher concentration of micelles. In the system with dimeric surfactant (n=2) alkanediyl-,ω-bis(dimethyldodecylammonium bromide) referred to as 12-s-12, the hyaluronate–surfactant interaction was observed at low surfactant concentration, opposite to the case of NaHA-NaCl-monomeric surfactant. In certain range of surfactant concentration, viscosity of the system can be fairly good described by the empirical Jones–Dole equation. However, the fit fails at high surfactant concentration. From the rheological measurements follows that NaHA aqueous solution shows non-Newtonian behaviour. When adding NaCl and shearing, viscosity increases as a result of affecting the ion atmosphere which surrounds micelles, by shearing. The same effect was observed in the system NaHA-NaCl-ammonium surfactant (both monomeric and dimeric). The hyaluronate–surfactant interaction is assumed at low shearing. The influence of surfactant structure on viscosity at the same NaCl concentration shows that the increasing value of the carbon number in spacer of dimeric surfactant increases viscosity and stretches the hyaluronate coils.