Interaction of Alkyltrimethylammonium Surfactants with Polyacrylate and Poly(styrenesulfonate) in Aqueous Solution: Phase Behavior and Surfactant Aggregation Numbers

Abstract

The interactions between polyacrylate and cationic surfactants has been studied. Aggregation numbers of dodecyltrimethylammonium (DoTA+) micelles formed in very dilute aqueous solutions of polyacrylate have been estimated with time-resolved fluorescence quenching, using as quencher dodecylpyridinium ion, which is distributed similar to DoTA+ between micelle and water subphases. The aggregation numbers (=65) were found to be the same as in 50 mM dodecyltrimethylammonium bromide (DoTAB) solutions. The distribution of the quencher between micelles and water was also investigated. It was concluded that the quencher and the surfactant mixed ideally in the micelles. The effect of salt on the phase behavior in aqueous solutions of polyacrylate together with DoTAB, dodecyltrimethylammonium chloride (DoTAC), cetyltrimethylammonium bromide (CTAB), or cetyltrimethylammonium chloride (CTAC) has been investigated. The concentration of surfactant and the aggregation number in both of the coexisting phases in the two-phase region of the phase diagram were estimated. The aggregation numbers (about the same in dilute and concentrated phases) for DoTAB, DoTAC, and CTAC, were approximately 80, 70, and 150, respectively. CTAB formed rodlike micelles in all investigated phases. We found that both the choice of salt and the size of the micelles were important for the extension of the two-phase region. Sodium polyacrylate -CTAB showed a segregative phase behavior at high concentrations of salt. The phase behavior of the system sodium poly(styrenesulfonate)-DoTAB-water was also investigated. The system was found to behave differently in many respects from the system with polyacrylate and the same surfactant. The critical aggregation concentration in dilute solutions ofPSS was estimated from surfactant selective electrode measurements and was found to increase with the concentration of the polyelectrolyte. Phase separation started at the same PSS-DoTAB ratio (®=1) in both dilute and concentrated solutions.

Interactions between cationic starch and anionic surfactants

“…This reduces the tendency to associative phase separation. The salt effects have been confirmed for mixtures of cationics with NaPa (sodium poly(acrylate)) by (Hansson and Almgren, 1994). They suggested that the increasing cec with increasing surfactant chain length could be attributed to a larger aggregation number of micelles.…”

“…The N agg values for polyelectrolyte-bound aggregates increase with the surfactant chain length as in polymer-free systems (Almgren et al, 1992), but decrease with temperature (Hansson and Almgren, 1995) and are independent of the nature of the surfactant counterion (Hansson and Almgren, 1994) and of the added electrolyte (Hansson and Almgren, 1995). Thus, there is series of results in contrast with the behaviour of polymer-free surfactant solutions.…”

“…Almgren et al have performed extensive determinations of N agg for variety of systems (NaPSS/C n TAB and C n TAC (Almgren et al, 1992); NaPAA or NaPSS and C n TAB (Hansson and Almgren, 1994); NaPVS or NaDXS and C 12 TAB (Hansson and Almgren, 1995); NaHy and C 10 TAB or C 12 TAB (Thalberg et al, 1991 a, d). The N agg values were found to be close to those for polymer-free aggregates for PS1("=1)/C 12 TAC, NaPAA/C 12 TAB, NaHy/C 12 TAB and NA-CMA (sodium carboxyamylose)/C 16 TAB (Zhen and Tung, 1992).…”

Micellar liquid chromatography of polycyclic aromatic hydrocarbons: Alkylpyridinium chloride as mobile phase modifier and selective fluorescence quencher

“…The pyridinium and trimethylammonium head groups are similar in many aspects, such as the central atom. Therefore, ideal mixing of CPC and CTAC has been assumed experimentally and theoretically [57,58,60,61]. Small deviations from ideality will be expected for DDPC and CTAC mixing, because of the four-carbon difference in their tails.…”

“…Therefore, cetyltrimethylammonium chloride (CTAC), which is not a PAH selective fluorescence quencher but with similar properties to CPC and DDPC, is used as a cosurfactant. The presence of CTAC allows the quencher concentration in micellar phase to be adjusted with little change to micelles [41,57,58].…”