N-Alkyltrimethylammonium

TABLE 2 81Br NMR parameters of n-alkyltrimethylammonium bromide salts averaged over a range of MAS frequencies 6... 

Ryoo[189] found that the structural order of MCM-41 can be improved remarkably if mixed surfactants of n-alkyltriethylammonium bromides (CrcTEAB, n = 12,14,16,20 and 22), and n-alkyltrimethylammonium bromides (CrcTMAB) are used. The optimum mixing ratio can be tuned according to the length of the alkyl groups. 

A series of n-alkyltrimethylammonium halides that shows a well-resolved condis state has been described recently The results of thermal analyses on these com-... 

Iwamoto K, Ohuki Y, Sawada K, Seno N (1981) Solid-solid phase transitions of long-chain n-alkyltrimethylammonium halids. Md. CrysL liq. Cryst., 73 95... 

So far, only experimental observations based on SERS measurements, which were reinforced by ab inito calculations, have been presented. From their interpretation the corresponding adsorption geometries for n-alkylpyridi-nium and n-alkyltrimethylammonium were proposed. But up to now, no reasons have been presented to explain why is one case the surfactant is adsorbed on the Ag-surface with its tail directed away from the electrode, and in the other case the adsorpton succeeds with the tail running parallel to the electrode surface. 

Quats are included in the list of surfactants for EOR, but technically they are used in other oil field operations, particularly in drilling muds. Their cationic nature, ability to emulsify oils plus potent germicidal activity make quats uniquely useful in mineral processing and oil applications. There is an abundance of environmental data on quats, not because of oil field operations, but rather because of their use as fabric softeners in detergents. The best known fabric softener and antistatic agent is ditaUow dimethyl ammonium chloride (DTDMAC). Emulsifiers commonly have a N-alkyltrimethylammonium chloride or N-alkylimidazoline chloride configuration, and germicides, such as benzalkonium chloride, typically have a N-alkyldimethylbenzylammonium chloride structure. The fate and effects of these multifunctional surfactants are detailed in several reviews [9, 55, 60, 61]. 

Fig. 3.7.1 Variation of (a) surface tension % and (b) critical surface tension 7c of surfactant treated glass surfaces with increasing carbon content of the surfactant alkyl chain, (a) Surface tension Jb for substrates with n-alkyl monoamine layers [6]. (b) Critical surface tension for substrates with n-alkyltrimethylammonium bromide layers [7].

Alonso, B., Massiot, D., Florian, R, Paradies, H. H., Gaveau, R, and Mineva, T. (2009). N and Br. Quadrupolar nuclei as sensitive NMR probes of n-alkyltrimethylammonium bromide crystal structures. An experimental and theoretical study. J. Phys. Chem. B. 113, 11906-11920. 

Table 21 Br SSNMR parameters for n-alkyltrimethylammonium bromide salts CxH2x+i(CH3)3N Br- from Alonso et at. [44]...

Five n-alkyltrimethylammonium bromide C H2 +i(CH3)3N Br salts (x=l, 12, 14, 16, 18) were characterized by and Br MAS SSNMR in order to determine their NMR parameters and provide insight into their crystal structures (Table 21) [44]. Diffraction data and computations were also used in a complementary manner. The combined use of both and Br NMR data proved to be useful for structure refinement due to the fact that the NMR parameters were found to be strongly dependent on the chain packing among the five samples, more specifically variations in C-N-C angles and in the spatial positioning of the cations and anions. 

The Raman spectra of n-hexyl, n-octyl, n-decyl, and n-dodecyl trimethyl-ammonium bromides in the 150-600 cm" region are shown in Fig. 1. Strong Raman bands are observed for all of these in the 160-300 cm region, and these shift markedly to a lower frequency with an increase in chain length. We may assign the bands observed at 251, 208, 179, and 164 cm to the accordion modes of the n-hexyl, n-octyl, n-decyl, and n-dodecyl chains, respectively. Figure 2 shows the linear relationship between the accordion band frequency and the reciprocal number of carbon atoms (1/Cn) for the fom n-alkyltrimethylammonium bromides. We may assume that the accordion band frequencies of the n-octyl, n-decyl, and n-dodecyl chains,... 

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