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Alkylammonium cationic surfactant

Except for the PBS/SAP-qC16 (n-hexadecyl tri-n-butyl phosphonium cation modified saponite) system, the degree of degradation is the same for other samples. This indicates that MMT or alkylammonium cations, and at the same time other properties, have no effect on the biodegradability of PBS. The accelerated degradation of PBS matrix in the presence of SAP-qC16 may be due to the presence of alkylpho-sphonium surfactant. This kind of behavior is also observed in the case of PLA/MMT-based nanocomposite systems. [Pg.294]

The electrostatic and steric effects can be combined to stabilize nanoparticles in solution. This type of stabilization is generally provided by means of ionic surfactants such as alkylammonium cations (Scheme 9.3). These compounds bear both a polar head group which is able to generate an electrical double layer, and a lipophilic side chain which is able to provide steric repulsion [14, 15]. [Pg.219]

Linfield, W.M. 1970. Straight chain alkylammonium compounds. In E. Jungermann, ed., Cationic Surfactants, Surfactant Science Series, Vol. 4, pp 9-70. Marcel Dekker, New York. [Pg.466]

Structure of Br may not be the same as that of the bulk. Some of the molecular dynamics calculations predict that halide anions in water tend to float on the surface of clusters consisting of water molecules rather than within water. This effect may cause a dissimilar solvation structure to that of the bulk. In addition, if the anion is segregated at the surface by surfactants such as large alkylammonium cations, the anion density at the surface should be high and its environment differ from the bulk. This is a preliminary report of the first experimental study of the solution surface by the EXAFS technique. This technique provides us information on the gas/liquid interface, the structure of Langmuir films, and the effect of the interface on chemical reactions. [Pg.246]

Polymers may adsorb readily on solid surfaces. Somasundaran et al. (1964) have investigated the effect of chain length on the adsorption of alkylammonium cations and of surfactant anions on oxide surfaces. These authors consider that the adsorption is influenced by the van der Waals energy of interaction or... [Pg.581]

Cationic surfactant of the alkylammonium bromide type the alkyl chain contains x carbon atoms... [Pg.164]

The alternative use of cationic surfactants (quaternary alkylammonium salts) is recommended to increase retention of highly hydrophilic compounds. Cationic surfactants reverses the EOF. As the cationic micelles migrate electrophoretically against the anodic EOF, an extended migration window results. An example of MEKC separation using cationic surfactants is the analysis... [Pg.915]

One of the first major surveys into the phase behavior of cationic surfactants was done by Blackmore and Tiddy who did penetration scans on a variety of surfactants including the -NH, NMej, NEtj, NPr and NBu series [151]. Previous studies had mostly been limited to alkylammonium and alkylmethylammonium salts [152, 153]. These show a qualitatively similar behavior to that of the anionic systems, with the sequence H,/V,/Lo( for short chain derivatives being replaced by Hi/lnt/Lj, for long chain compounds. For the intermediate chain lengths, V, phases replace the intermediate structures as temperature increases. [Pg.377]

Electrostatic and steric stabilization are, in a sense, combined in the use of long-chain alkylammonium cations and surfactants, either in single-phase sols or in the reverse micelle synthesis of colloidal metals. [Pg.218]

There are a variety of cationic surfactants other than quaternary alkylammonium salts. Accordingly, complex formation of 1-hexadecylpyridinium bromide (CPB) was attempted (Figure 4.44). After many trials, ten complex crystals were obtained, two of which were suitable for X-ray analysis, i.e. with guaiacol (XXXIII) and 9-anthracenecarboxylic acid (XXXTV) (Figure 4.44). The two crystals are isostructural. [Pg.134]

The layered silicate nanoparticles are usually hydrophilic and their interactions with nonpolar polymers are not favorable. Thus, whereas hydrophilic polymers are likely to intercalate within Na-activated montmorillonite clays [24-29], hydrophobic polymers can lead to intercalated [23,30-32] or exfoliated [33] structures only with organophilized clays, i.e., with materials where the hydrated Na+ within the galleries has been replaced by proper cationic surfactants (e.g., alkylammonium) by a cation exchange reaction. The thermodynamics of intercalation or exfoliation have been discussed [34-37] in terms of both enthalpic and entropic contributions to the free energy. It has been recognized that the entropy loss because of chain confinement is compensated by the entropy gain associated with the increased conformational freedom of the surfactant tails as the interlayer distance increases with polymer intercalation [34,38], whereas the favorable enthalpic interactions are extremely critical in determining the nanocomposite structure [39]. [Pg.366]

In general, pristine MMT contains hydrated Na or ions. Therefore, they are only miscible and compatible with polar polymers. In order to make it compatible with hydrophobic polymers, the interlayer cations are exchanged with quaternary alkylammonium cations through ion-exchange reaction. Ion-exchange reactions can be done with several cationic surfactants including primary, secondary, tertiary, and quaternary alkylammonium or alkylphos-phonium cations. ... [Pg.246]

Three pyrrolidinium-based ionic liquids - N-dodecyl-N-methylpyrrohdi-nium bromide, N-butyl-A-octylpyrrolidinium bromide, and iV-butyl-iV-dodecylpyrrolidinium bromide - were synthesized and eharaeterized by their decomposition temperatures (Td) measured by TGA, and by their m.p. (Tm), glass transition (Tg) and crystaline temperatures (Teryst) detected by DSC. Their self-aggregation properties in aqueous solution were studied and their behavior is compared with that of analogous conventional cationic surfactants, tetra-alkylammonium bromide salts. Taylor dispersion... [Pg.494]

Symmetrical catanionic surfactants consist of anionic and cationic surfactants of the same chain length. Alkylammonium alkyl sulfates [such as decylammonium decyl sulfate (DeADeS), dodecylammonium dodecyl sulfate (DDADDS), and tetradecylammonium tetradecyl sulfate (TDATDS)] are prepared by mixing equimolar solutions of alkylammonium chloride and the corresponding alkyl sulfate. The reaction can be represented as... [Pg.460]

Quaternary alkylammonium salts or alkylamines are the cationic surfactants most commonly used in the modification of layered silicates. They are synthesized by complete alkylation of ammonia or amines. Many efforts have been made to produce ammonium surfactants to improve the affinity between the clay mineral and the polymer [3]. Ammonium organoclays undergo thermal degradation at temperatures below or comparable to the melt-processing temperatures of many polymers. [Pg.69]

Alkylammonium salts are typical cationic surfactants. The adsorption and the properties of the monolayers formed by these salts at water-air and water-oil interfaces have frequently been investigated [11, 24, 36, 37, 46, 63]. Mostly the adsorption of alkylammonium cations from the aqueous phase was studied. Special attention was paid to the relation between the structure of alkylammonium cations, their surface-active properties and the monolayer structure. Less attention was given to the influence of the anion nature of alkylammonium salt adsorption from the non-aqueous phase and competitive adsorption of counterions in cationic monolayers at the water-oil interface, although these problems are vital for understanding the mechanism of liquid ion-exchange extraction. [Pg.184]

The surface activity of the soluble cationic surfactants at the water-air and water-nonpolar oil interfaces is mainly determined by the structure of the hydrocarbon chains. The work of adsorption in the homologous series of alkylammonium salts obeys the Traube rule [24,46,63,76]. Shipunov studied adsorption in the homologous series of tetra-alkylammonium chlorides at the water-heptane interface. He established that the work of adsorption is proportional not to the number of methyl groups in the... [Pg.185]

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]. [Pg.186]

In the extraction systems the surfactant is distributed between the phases. Boguslavsky et al. systematically studied the adsorption of tetra-alkylammonium salts in such systems at the water-nitrobenzene interface [11, 76, 90, 91]. The values of the Volta potential at this interface are consistent with the thermodynamic distribution theory. The adsorption isotherms are formally described by the Frumkin equation with the increasing size of tetra-alkylammonium cation, the repulsion between the adsorbate particles increases. It testifies to the fact that the cations of alkylammonium... [Pg.186]

The influence of the host phase was checked for some homologues of the anionic alkylammonium halides as well as the cesium and ammonium salts of perfluoiinated carbon acids which are cationic surfactants. The results can be summarized by two statements (i) the longer the alkyl chain of the surfactant, the smaller the twist and (ii) the bulkier the head group of the surfactant, the smaller the twist, see Figure 14.14. [Pg.468]

Washall [566] has reviewed analytical pyrolysis of cationic alkylammonium halide surfactants and has shown that analytical pyrolysis is a technique that works well even with trace quantities (low ppm level). For applications which require protection of sample integrity, as in forensic science and in art conservation, analytical pyrolysis is an obvious analytical tool. Bart [563] has reviewed polymer/additive analysis by flash pyrolysis techniques and Challinor [567] the applications of analytical pyrolysis in forensic science. Paints, varnishes, glues, pigments, waxes, organic binder formulations have been studied from the aspects of both conservancy and authentication. [Pg.222]

As mentioned before, the most common cationic surfactants used in the organo-modification are the quaternary alkylammonium salts, which are generally synthesized by complete alkylation of ammonia or amines. Figure 7.4 presents some examples of these alkylammonium salts. [Pg.154]

In order to render the silicate layer surface more organophilic and thus more compatible with the polymer matrix, these intercalated alkaline cations can be exchanged with cationic surfactants such as alkylammonium or alkylphosphonium ions" . ... [Pg.329]


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