Hydrophobe chain-length effect

For the sake of brevity, salient aspects of key structure-activity relationships in one homologous series of twelve mono- and bis-acyl homologated spermine analogues (Fig. 12.8) will be first discussed (Miller et al., 2005). We addressed two questions in this study (i) what is the optimal hydrophobic chain length for effective anti-endotoxic activity, (ii) are symmetrical bis-acyl spermines more effective than mono-acyl compounds We found that a carbon number of 14-16 is optimal in mono-acyl spermines (Fig. 12.9) which are, in general, as potent as... 

With the slow demise of the nonylphenol ethoxylate market due to legislation, the fatty alcohol market has the chance to design alternatives by subtle changes to the hydrophobe chain lengths and alkoxylate levels. The effects must be achieved with biodegradability as... 

Kunieda, H., Uddin, M.H., Horii, M., Furukawa, H. and Harashima, A. (2001) Effect of hydrophilic- and hydrophobic-chain lengths on the phase behavior of A-B-type silicone surfactants in water. /. Phys. Chem. B, 105(23), 5419-26. 

We have examined the stmcture of both ionic and nonionic micelles and some of the factors that affect their size and critical micelle concentration. An increase in hydrophobic chain length causes a decrease in the cmc and increase of size of ionic and nonionic micelles an increase of polyoxyethylene chain length has the opposite effect on these properties in nonionic micelles. About 70-80% of the counterions of an ionic surfactant are bound to the micelle and the nature of the counterion can influence the properties of these micelles. Electrolyte addition to micellar solutions of ionic surfactants reduces the cmc and increases the micellar size, sometimes causing a change of shape from spherical to ellipsoidal. Solutions of some nonionic surfactants become cloudy on heating and separate reversibly into two phases at the cloud point. 

For POE nonionics, (1) the ratio increases with increase in the number of OE units in the POE chain at constant hydrophobic chain length, the effect becoming less pronounced as the number of EO units increases, and (2) the ratio decreases with increase in the length of the alkyl chain, at constant number of EO units in the POE chain. The first effect is due to the increase in the size of the hydrophilic head... 

Lipophilic linkers (Salager, 1998) and hydrophilic linkers (Uchiyama, 2000 Acosta, 2002) are used to increase the value of SP and decrease y. Lipophilic linkers are long-chained alcohols (above C8) and their low oxyethylenation products that increase the surfactant-oil interaction. The most effective ones have hydrophobic chain lengths that are an average of the hydrophobic chain length of the surfactant and the chain length of the alkane oil. Hydrophilic linkers increase the surfactant-water interaction. Examples are mono- and dimethylnaphthalene sulfonates and sodium octanoate... 

In cationic surfactants, the presence of short-chain alkyl groups (fewer than four carbon atoms) attached to the nitrogen seem to have little effect on the efficiency of adsorption of the molecule. The dominant factor will always be the length of the primary hydrophobic chain. That effect is true regardless of whether the alkyl groups are attached to a quaternary ammonium group, an amine oxide, or a heterocyclic nucleus such as pyridine. 

EIN Einaga, Y., Kusumoto, A., and Noda, A., Effects of hydrophobic chain length on the micelles of heptaoxyethylene hexadecyl C16E7 and octadecyl C18E7 ethers, Polym. J.,... 

Tirtaatmadja V, Tam KC, Jenkins RD. Rheological properties of model alkali-soluble associative (BASE) polymers effect of varying hydrophobe chain length. Macromolecules 1997 30 3271-3282. 

From the experimentally determined eme s of the binary surfactant mixtures, as well as the eme s of the individual surfactants, the p parameter was calculated.[4] The p parameter reflects the net interaction between two surfactants, and the stronger the attraction, the more negative is the p parameter. Here, surfactants with the same hydrophobic chain length have been studied, so the effects refer to the interactions between the head groups.[10] First, using the fact that ZxJ" = 1, the mole fraction of surfactant i in the micelle, was calculated by iteration... 

Varga et al. measured surface tension at room temperature of aqueous solutions of oxalic, malonic, succinic, glutaric, adipic, maleic, malic, citric, and c/s-pinonic acid [96]. Surface tension decreased with increasing hydrophobic chain length. c -Pinonic acid was found to decrease the surface tension effectively over a wider range of concentrations than the other organics. 

Not all surfactants have the same effect on skin permeability this depends on their ionic charge, hydrophobic chain length, their water/oil partition coefficient, and so forth. A good comparative review of surfactants has been performed by Walters et al. [26]. Additional details are also given in Chapter 11 of this volume. 

Increase in the length of the polyoxyethylene chain of non-ionic surfactants at a constant hydrophobic chain length results in a decreased surface activity. This effect is clearly shown in Fig. 1.1 for a series of non-ionic surfactants with the general formula CH3(CH2)i5(OCH2 CH2) OH. 

Symmetrical (two equal fatty acid chains) (Figure 5.4, 1) and asymmetrical (two different fatty acid chains) (Figure 5.4, 2) nonionic double-chain surfactants of the type A ,A -diacyl lysine polyoxyethylene glycol amide compounds, with a structural resemblance to natural lecithin phospholipids, have been reported by the authors lab [35-38] to determine the effect of several structural parameters (hydrophobic chain length, polyoxyethylene (POE) chain length and number of polyoxyethylene chains) on the physicochemical properties and biological performance of these natural mimics. 

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