NOTE
First Evidence of Poly(ethylene oxide)-Mixed Sodium Dodecyl Sulfate/Sodium Decyl Phosphate Complexes the absence of NaDeP in PEO binding, and reports conductometric and kinetic results of ideal mixing of SDS and NaDeP for PEO.
Polymer-mixed surfactant complex formation among poly(ethylene oxide), sodium dodecyl sulfate, and sodium decyl phosphate was identified using conductivity measurements and following the EXPERIMENTAL kinetics of the acid-catalyzed hydrolyses of di-tert-butyl and din-butyl benzaldehyde acetals. By conductivity, the onset of the Substrates di-tert-butyl acetal (BTBA) and di-n-butyl benzaldehyde acemixed complexation, the critical aggregation concentration, foltal (BBA), PEO (Aldrich) weight-average molecular weight 10,000, and sodium dodecyl sulfate (Sigma, 99%) are as in previous investigations (1, lows an ideal mixing behavior in the same way as takes place in 4). Molar concentrations of PEO are given on a monomer basis (moles of the absence of polymer, previously investigated. The reaction of monomer per liter of solution), and the stock solutions were routinely di-tert-butyl benzaldehyde acetal is generally acid catalyzed, and prepared under magnetic stirring for at least 12 h prior to use. NaDeP was the first-order rate constant increases linearly up to ca. 0.5 mole prepared as previously described (1, 11).
fraction of sodium decyl phosphate; however, as the hydrolysis of
Hydrolyses were performed by adding 5 ml of BTBA or BBA from a di-n-butyl benzaldehyde acetal is specifically hydrogen ion cata-0.002 M stock solution prepared in dry acetonitrile into 2.50 ml of 0.050 lyzed, the rate constant is independent of the mole fraction of the M succinate buffer solution, pH 6.00, at 25.00 { 0.02ЊC, containing appro- phosphate surfactant. ᭧ 1997 Academic Press priate polymer and surfactant concentrations. Formation of benzaldehyde, Key Words: polymer surfactant interaction; surfactant mixture; in both hydrolysis reactions, was followed spectrophotometrically at 252 acetal hydrolyses; conductivity; poly(ethylene oxide); sodium denm using a Hewlett-Packard 8452-A diode array spectrophotometer. Rate constants were calculated using Hewlett-Packard 89532-K software. Stan-cyl phosphate.
dard deviations for log(A ϱ 0 A)-vs-time plots were less than 10 04 .
Conductance measurements were carried out as in previous investigations (3, 5, 10); however, we emphasize the quality of our results because the software permits us to take up to 2000 points within the concentration range