Discrepancies over the onset of surfactant monomer aggregation interpreted by fluorescence, conductivity and surface tension methods

Abstract

Molecular probe techniques have made important contributions to the determination of microstructure of surfactant assemblies such as size, stability, micropolarity and conformation. Conductivity and surface tension were used to determine the critical aggregation concentration (cac) of polymer-surfactant complexes and the critical micellar concentration (cmc) of aqueous micellar aggregates. The results are compared with those of fluorescent techniques. Several surfactant systems were examined, 1-butanol-sodium dodecylsulfate (SDS) mixtures, solutions containing poly(ethylene oxide)-SDS, poly(vinylpyrrolidone)-SDS and poly(acrylic acid)-alkyltrimethylammonium bromide complexes. We found differences between the cac and cmc values obtained by conductivity or surface tension and those obtained by techniques which use hydrophobic probe

Synergistic Behavior of Anionic Surfactants and Hydrolyzed Polyacrylamide under an Extensional Field: Effect of Hydrophobicity

“…In the absence of the surfactant, the surface tension of HPAM 3630 was 73 mN/m, whereas the surface tension values of C-319 and D-118 were 55 and 51 mN/m, respectively (Table and Figure ). It is to be noted that D-118 with lesser surface tension values has a higher number of hydrophobic groups when compared to HPAM 3630 and C-319 that have zero or lesser hydrophobic groups . These observations indicate that the associative polymer has higher surface activity than HPAM 3630 and the one with a higher number of hydrophobic groups contributes to higher surface activity.…”

“…It is to be noted that D-118 with lesser surface tension values has a higher number of hydrophobic groups when compared to HPAM 3630 and C-319 that have zero or lesser hydrophobic groups. 55 These observations indicate that the associative polymer has higher surface activity than HPAM 3630 and the one with a higher number of hydrophobic groups contributes to higher surface activity. In Figure 3, it can be seen that there was no change in the surface tension value after 0.1 wt % for all the systems, which indicates that surfactant activity minimizes and polymer chains become saturated.…”