Catalytic Spectrophotometric Determination of Ultratrace Amounts of Silver with Solubilizing Effect of Nonionic Surfactant

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Interaction of Fluorocarbon Containing Hydrophobically Mdified Polyelectrolyte with Nonionic Surfactants

The interaction of fluorocarbon containing hydrophobically modified polyelectrolyte(FMPAANa) with two kinds of nonionic surfactants(hydrogenated and fluorinated)in a semidilute (0.5wt%) aqueous solution had been studied by rheological measurements,Association behavior was found in both systems.The hydrophobic interaction of FMPAANa with fluorinated surfactant(FC171) is much stronger than that with hydrogenated surfactant(NP7.5) at low surfactoant concentrations.The interaction is strengthened by surfactants being added for the density of active junctions increased.Whereas distinct phenomena for FC171 and NP7.5 start to be found as the surfactants added over their respective certain concentration.The interaction of polyelectrolyte with fluorinated surfactant increases dramatical ly while that with hydrogenated surfactant decreases.     

Aminolysis ofO-alkylO-4-nitropyenyl chloromethylphosphonates in reverse micellar solutions of the nonionic surfactant

The reaction ofn-hexylamine withO-alkylO-4-nitrophenyl chloromethylphosphonates in toluene solutions of poly(ethylene glycol)-600 monolaurate (PM) has been studied by spectrophotometry. The reverse micelles of the nonionic surfactant increase more than tenfold the observed rate constant of aminolysis. The catalytic activity of the surfactant is practically independent of the alkyl radical length of phosphonate. An increase in the concentration of amine results in a decrease in the catalytic efficiency. The character of the dependence of the rate constant on the concentration of PM is affected by the alkyl chain length of the substrate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1735–1738, September, 1998.     

Micellar and Mixed-Micellar Effects on Alkaline Hydrolysis of tris(1,10–phenanthroline)iron(II): Kinetic Exploration

The kinetics of alkaline hydrolysis of tris(1,10–phenanthroline)iron(II) has been studied in the presence of nonionic and mixed nonionic–ionic micellar media at 308 K. The effects of mixed-micellar environments of nonionic with ionic surfactants (C₁₂E₂₃/ATABs and C₁₂E₂₃/SDS) on the hydrolytic rate have been studied. The rate decreases monotonically with an increment of [C₁₂E₂₃]_T (total Brij 35 concentration) at constant [^?OH]₀ and has been discussed with the pseudo-phase micellar model. The rate also decreases with [C₁₂E₂₃]_T at a continuous addition of ionic surfactants (ATABs and SDS). The observed rate constant k_obs follows the empirical relation: k_obs = (k₀ + θK [C₁₂E₂₃]_T)/(1 + K [C₁₂E₂₃]_T) (where θ and K are empirical constants). The values of θ remain unaffected, whereas K decreases nonlinearly with [ATABs]_T in a mixed C₁₂E₂₃?ATAB micellar system. But the k_obs in a mixed C₁₂E₂₃–SDS micellar system is much lower than that of the C₁₂E₂₃–ATAB system and do not comply with any micellar kinetic models.     

Effect of Polymer on Dynamic Interfacial Tensions of Anionic–nonionic Surfactant Solutions

The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer systems against n-decane have been investigated using a spinning drop interfacial tensiometer in this paper. Two anionic–nonionic surfactants with different hydrophilic groups, C₈PO₆EO₃S (6-3) and C₈PO₆EO₆S (6-6), were selected as model surfactants. Partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed. The influences of surfactant concentration, temperature, polymer concentration, and oleic acid in the oil on IFTs have been studied. The experimental results show that anionic–nonionic surfactants can form compact adsorption films and reach ultralow IFT (10^?3 mN/m) under optimum conditions. The addition of polymer has great influence on dynamic IFTs between surfactant solutions and n-decane mainly by the formation of looser mixed films resulting from the penetration of polymer chains into the interface. The compact surfactant film will also be weakened by the competitive adsorption of oleic acid, which results in the increase of IFT. Moreover, the penetration of polymer chains will be further destroyed surfactant/polymer mixed layer and lead to the obvious increase of IFT. On the other hand, polymers show little effect on the IFTs of 6-6 systems than those of 6-3 because of the hindrance of longer EO chain of 6-6 at the interface.     

Self aggregation of binary mixtures of sodium dodecyl sulfate and polyoxyethylene alkyl ethers in aqueous solution

The mixed micelles of sodium dodecyl sulphate (SDS) with Brij35 and Brij 97 were studied separately by fluorescence measurement using pyrene as fluorescent probe. In the range of 0–1.0 mole fraction (X) of added SDS to Brij solutions, the cmc value of the mixed micelles varies from 0.085 to 8 mmol with Brij 35 and 0.04 to 8 mmol with Brij 97. The aggregation number also changes. A measure of the stability of mixed micelles is also presented. The interaction parameter ₁₂ and the chain–chain contribution parameter (B₁) are extracted from the analysis of the results. This parameter B₁ is related to the standard free energy change associated with the introduction of one ionic species into a nonionic micelle coupled with the release of one nonionic species from the micelle. The clouding behaviour of Brij 97 in the presence of SDS was investigated and the associated thermodynamic parameters of clouding were generated and discussed.     

Effects of Nonionic, Cationic, and Mixed Nonionic-Cationic Surfactants on the Acid-Base Behavior of Phenyl Salicylate

The effects of Brij 35 micelles, CTABr micelles, and mixed Brij 35–CTABr micelles on the acid–base behavior of phenyl salicylate (PST) have been studied in aqueous solution containing 2% v/v acetonitrile. The apparent pK_b (pK^app_b) of PST is decreased by 1.5 pK units with the increase in [Brij 35] from 0 to 0.02 M which is attributed to micellar medium effect. The values of pK^app_b remain almost independent of [CTABr] within its range 0.01–0.03 M. The increase in [CTABr] from 0 to 0.03 M in aqueous solution containing 0.02 M Brij 35 has not resulted in a change in pK^app_b. This shows that the characeristic structural features of nonionic Brij 35 micelles remain essentially unchanged on addition of CTABr under the present experimental conditions.     

The adsorption structure of nonionic surfactant on the sessile mercury electrode in a thin liquid film

In relation to a colloid stability, the adsorption structure of the Stern layer on a sessile mercury electrode in a thin liquid film of nonionic surfactant was investigated by measuring the double layer capacitance. The Stern capacitance on the electrode in the film could be detected when the measuring frequency used was low, for the resistance of the film was not extremely high but of the order of several thousand ohm. It was found that the adsorption structure of nonionic surfactant in the thin liquid film shows a stratification different from that of bulk.     

Nonionic surfactant-selective electrode and its application for determination in real solutions

A liquid membrane nonionic surfactant sensitive electrode has been prepared, based on a new barium pseudocationic complex of a highly ethoxylated fatty alcohol polyglycol ether and tetraphenylborate as sensing material. The complex has been incorporated into the plasticized PVC-membrane and used as sensing material.The electrode exhibited positive linear non-Nernstian response toward different nonionic surfactants and sub-Nernstian response toward tetraphenylborate with the lower detection limit of 3.3 × 10⁻⁷ mol dm⁻³ in barium chloride solution.The interfering effect of some alkaline, alkaline earth, and heavy metal cations, has been demonstrated by displaying their calibration curves compared with that of Triton X-100.The electrode has been used as an end-point indicator for potentiometric titration of analytical and technical grade polyethoxylated nonionic surfactants, modelled detergent products, and commercial detergents.     

Direct Potentiometric Study of Cationic and Nonionic Surfactants in Disinfectants and Personal Care Products by New Surfactant Sensor Based on 1,3-Dihexadecyl−1H-benzo[d]imidazol−3-ium

A novel, simple, low-cost, and user-friendly potentiometric surfactant sensor based on the new 1,3-dihexadecyl−1H-benzo[d]imidazol−3-ium-tetraphenylborate (DHBI–TPB) ion-pair for the detection of cationic surfactants in personal care products and disinfectants is presented here. The new cationic surfactant DHBI-Br was successfully synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectrometry, liquid chromatography–mass spectrometry (LC–MS) and elemental analysis and was further employed for DHBI–TPB ion-pair preparation. The sensor gave excellent response characteristics for CTAB, CPC and Hyamine with a Nernstian slope (57.1 to 59.1 mV/decade) whereas the lowest limit of detection (LOD) value was measured for CTAB (0.3 × 10⁻⁶ M). The sensor exhibited a fast dynamic response to dodecyl sulfate (DDS) and TPB. High sensor performances stayed intact regardless of the employment of inorganic and organic cations and in a broad pH range (2−11). Titration of cationic and etoxylated (EO)-nonionic surfactant (NSs) (in Ba²⁺) mixtures with TPB revealed the first inflexion point for a cationic surfactant and the second for an EO-nonionic surfactant. The increased concentration of EO-nonionic surfactants and the number of EO groups had a negative influence on titration curves and signal change. The sensor was successfully applied for the quantification of technical-grade cationic surfactants and in 12 personal care products and disinfectants. The results showed good agreement with the measurements obtained by a commercial surfactant sensor and by a two-phase titration. A good recovery for the standard addition method (98–102%) was observed.