Alkylpyridinium surfactants

Similar to germanium sulfides or selenides, [Sn4Seio] adamantine clusters also exist and have been found to form mesostructured semiconductors with Pt + when templated by the lyotropic liquid-crystalline phase of alkylpyridinium surfactant [Ci6H33NC5H5]Br. This mesophase designated as CiePyPtSnSe has a band gap of 1.5 eV. 

The formation of rodlike micelles from spherical micelles of alkylpyridinium surfactants in aqueous solution is strongly dependent on the following (1) structure and hydrophobicity of counterion, (2) hydrophobicity and the type of substituent as well as the substituent pattern of the aromatic ring counteri-ons/additives, (3) the microenvironment of the counterion (substituent) in the Stem region, and (4) the structure of the surfactant monomer (i.e., the surfactant cation) where head group effects are proposed to be the main driving force for sphere-to-rodlike transition. ... 

Solid state electrodes selective for alkylpyridinium cations are used to study the binding of these surfactants cations, with Cq 2> and alkyl chainlengths,... 

K. Hayakawa and J.C.T. Kwak Surfacatant-Polyelectrolyte Interactions. 4. Surfactant Chain Length Dependence on the Binding of Alkylpyridinium Cations to Dextran Sulfate. J. Phys. Chem. 88, 1930 (1984). 

Mixtures of these surfactants with water result in solutions with unique properties that we want to consider. We will use the alkylpyridinium chlorides as examples. Figure 18.11 compares the osmotic coefficient 0, apparent relative molar enthalpy 4>L, apparent molar heat capacity Cp, and apparent molar volumes V as a function of molality for two alkylpyridinium chlorides in water.w19... 

Cationic surfactant of the alkylpyridinium bromide type the alkyl chain contains x carbon atoms... 

In the presence of 15% pentanol, large amounts of water can be solubilized into heptane or toluene solutions of Ci2-Ci6 alkylpyridinium or alkyltrimethylammo-nium bromides (Venable, 1985). In heptane/pentanol, the longer-chain surfactants appear to be more effective than the shorter ones, while in toluene/pentanol the shorter ones appear to be more effective. In both solvent mixtures, the pyridinium salts are more effective solubilizers than the corresponding trimethylammonium salts. All the quaternaries investigated were more effective than sodium dodecyl sulfate. 

Malovikova A, Hayakawa K, Kwak JCT. Surfactant—polyelectrolyte interactions. 4. Surfactant chain length dependence of the binding of alkylpyridinium cations to dextran sulfate. J Phys Chem 1984 88 1930-1933. 

Electrodes suitable for the potentiometric determination of surfactants are either specially designed liquid or solid membrane electrodes or ion-selective electrodes that in addition to being selective to a particular ion, also quantitatively respond to surfactants. For example, a nitrate ion-selective electrode responds to anionic surfactants, a calcium ion-selective electrode is sensitive to quaternary ammonium salts, and a barium ion-selective electrode can be used for assaying polyethoxylates [43], In some cases it is possible for one to perform potentiometric determination of a counter-ion, e.g. one can titrate alkylpyridinium chloride or bromide salts with silver nitrate solution using silver wire as an indicator electrode [38]. 

Figure 2.10. Chemical structure of complexes of poly(vinyl-A/-alkylpyridinium) with Methyl Orange and the Ethyl Orange (EO) with C12D and CieD surfactants.

Fig. 5 Residence time 7r of surfactants in micelles. Variation with the carbon number m of the surfactant alkyl chain for sodium alkylsulfates (A), potassium alkylcarboxylates (O).and alkylpyridinium chlorides ( ). Reproduced from Ref. [26].

A variety of cationic surfactants are derived from pyridine and imidazole, such as the alkylpyridinium salts and the alkyl imidazolidinium salts. These salts are very stable in aqueous solutions, but absorb UV light which makes them difficult to be used in MLC. Also, surfactants associating a nonionic polyoxyethylene chain with a cationic terminal group have been designed [5],... 

The first reported work using SERS as probe to investigate the adsorption of surfactants at the solid-liquid interface dated from the beginning of the 1980s. In their report. Heard et al. [15] have shown that SERS spectra could be obtained even at submonolayer converge from n-alkylpyridinium bromide adsorbed at Ag colloid surfaces. Dendramis et al. [16] have studied the adsorption of cetyltrimethylammonium bromide (CTAB) on copper electrode surfaces. They were able to determine the CTAB adsorption rates from aqueous solution and observed no changes in the spectra as the concentration was varied... 

Fig. 1 Calculated Raman spectra from A alkylpyridinium and B alkyltrimethylammonium. The hydrocarbon tail-length was varied between Cj and C, for each surfactant. For a better visualization, lorentzian envelopes with a fixed line-width of 8 1/cm for all Raman bands were used. The symmetric CH stretching mode for both species is marked using a vertical line and labelled with the corresponding frequency, i.e. 2875 1/cm...

The adsorption of ionic surfactant on metalic surfaces at the liquid-solid interface is influenced and controlled by many factors, such as the surfactant concentration, counterion concentration and surface charge. The effect of these factors on the adsorption of alkylpyridinium on silver surfaces studied by means of the SERS spectroscopy are presented and discussed in this section. 

Figure 4a shows a characteristic SERS spectrum from cetylpyridinium bromide (CiePyBr). This measurement was recorded at — 0.2 V vs. SCE, i.e. at a positively charged surface. With alkylpyridinium belonging to a class of cationic surfactant, the anions of the electrolyte solution may build a bridge to facilitate the adsorption of a positively charged molecule onto a positive surface. 

In this work, a good deal of information on the adsorption properties from two kinds of cationic surfactants (alkylpyridinium and alkyltrimethylammonium) have been obtained by combining SERS measurements and vibrational calculations based on Hartree-Fock methods. 

When an electric field was applied to a sheet of PAMPS gel suspended in an N-alkylpyridinium chloride (C PyCl) surfactant solution, the gel showed significant and rapid bending toward the anode (Fig. 13). Among the surfactants used, C, PyCI and CijPyCl induced intense, steady bending with a magnitude of 4-6 mm within... 

Reproducibility being a major concern, we repeated break-in and leach-out voltammograms after each primary measurement. Break-in was steadily represented by one speed constant and leach-out by three. The type of the surfactant whether it was an aliphatic quaternary ammonium salt (CTAB, DTAB), an V-alkylpyridinium compound (CPC, CPB), or a Gemini tenside - left its mark on the parameters of hydrophobization, pore structure - and as a result - the permeability of the film. 

The nature of the anion also affects the surface activity of the water-soluble cationic surfactants. The surface activity of tetra-butylammonium salts at the water-air and water-hexane interfaces reduces in the order iodiode > bromide > chloride [77,78]. Boguslavsky et al. reported that the adsorption equihbrium constant and the adsorption at the water-octane interface are higher for tetra-alkylammonium bromides as compared to chlorides [76,79]. The influence of the counterions on the adsorption of alkylpyridinium salts at the water-air interface was studied. It was estab-hshed that the salts lowered the surface tension in the sequence perchlorate > thiocyanate > iodide > bromide > chloride [80-83]. The anion influence on the work of adsorption was found to increase with the growth of the concentration of the surface-active salt [83]. 

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