Hydrocarbon chain length

Fig. XI-14. Effect of hydrocarbon chain length on the f potential of quartz in solutions of alkylammonium acetates and in solutions of ammonium acetate. (From Ref. 183.)...

In the absence of steric constraints in Eq. (1.24a) Eact will not vary. Eads and 9 are the parameters that significantly change with hydrocarbon chain length or zeolite. 

Let us first consider the lipid molecular structures required. First is the hydrophobic matching. The length of the hydrophobic chain determines the thickness of the hydrophobic part of the lipid bilayer, this should correspond closely to the dimension of the native membrane. As most biological membranes contain diacylglycerol lipids with hydrophobic chain lengths of 16 18 carbon atoms. Thus, synthetic lipids should possess relatively long hydrocarbon chain length, e.g., 16-18 carbon atoms. 

If the pore-mechanism applies, the rate of permeation should be related to the probability at which pores of sufficient size and depth appear in the bilayer. The correlation is given by the semi-empirical model of Hamilton and Kaler [150], which predicts a much stronger dependence on the thickness d of the membrane than the solubility-diffusion model (proportional to exp(-d) instead of the 1 Id dependence given in equation (14)). This has been confirmed for potassium by experiments with bilayers composed of lipids with different hydrocarbon chain lengths [148], The sensitivity to the solute size, however, is in the model of Hamilton and Kaler much less pronounced than in the solubility-diffusion model. 

However the reduction in biological activity with increasing hydrocarbon chain length beyond the optimum (Figure la) and the increase in biological activity on initially increasing the hydrophilic nature of the surfactants (Figure lb) requires elucidation, especially at lower concentrations. 

A parabolic relationship between membrane activity and lipophil-icity of nonionic surfactants is clearly established in series of surfactants in which either the hydrocarbon chain length or ethylene oxide chain length is varied. Activity at low and high concentrations should be considered separately. 

Ionic surfactants actually only form micelles when their hydrocarbon chains are sufficiently fluid, that is at temperatures above their chain melting temperature. Below a specific temperature for a given surfactant, the Krafft temperature, the surfactant becomes insoluble rather than self-assembles. For CTAB this temperature is around 20 °C and only above this temperature are micelles formed. In general, the longer the hydrocarbon chain length, the higher the Krafft temperature. For this reason, shorter-chain-length surfactants or branched chain soaps... 

Present investigation was undertaken to elucidate the relationships between the nonaethoxylated fatty alcohols with different distributions of hydrocarbon chain lengths and surface adsorption,... 

For solutions of AEg with different distributions of hydrocarbon chain lengths, the Y log C curves appear to be different than mono-component system. The surface pressure at critical micelle concentration (iTcjic) AEg with a long hydrocarbon chain (C gEg) is Increased by adding the short AEg, but the effect is not significant if the hydrocarbon chain is in a wide distribution (i.g. coconut fatty radical) (Figure 2,3,4). As for the efficiency of surface tension reduction there is a synergestic effect for the mixed... 

From data listed in Table IV one sees 6 < 0, fj l <1, and H <0 which indicate that the micellization of a binary mixture with different hydrocarbon chain lengths is different than the case of ideal... 

The foam stability of mixed AEg with a middle chain length distribution is better than the individual lower one. Among all AEg, the mixed Cio,12 9 gives probably the best result on the stability of emulsion to caster oil. Introducing a long hydrocarbon chain in the mixture or a wide distribution in hydrocarbon chain length causes no effect on the emulsion stability (Figure 6). 

Figure 5. Relationship of AG and average hydrocarbon chain length (m). The dashed lines are the theoretical value, the plotted points experimental data, o-single component, o-binary mixture.

Figure 7. Relationship of solubilization and the average hydrocarbon chain length.

Polymerized olefins include poly-a-olefins (PAOs), linear a-olefins (LAOs), and internal olefins (IOs) [24]. Hydrocarbon chain length and branching are selected to optimize the drilling properties and minimize the environmental toxicity [20]. 

The membrane potential increased with increasing hydrocarbon chain length. Figure 7 shows the transport rate constants of various phosphonium ions as a function of the membrane potential. The selectivity coefficient of tpp+ has also been determined using a nitrobenzene—based membrane electrode45 a value of log KPot = 8.75 was reported, which is lower than that obtained with the arsenic analogue. 

Figures 2, 3, and 4 are semilogarithmic plots of k8 vs. tt for alkyl sulfate, phosphonate, and carboxyl monolayers, respectively, at various pH s and for two different hydrocarbon chain lengths. The points are the...

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