Dodecyl dimethyl phosphine oxide

To demonstrate the applicability of the criterion, given by Eqs (5.8) - (5.10), Ay(t )-values of aqueous solutions containing decyl dimethyl phosphine oxide as the main component and dodecyl dimethyl phosphine oxide as the simulated impurity were measured. The results, shown in Fig. 5.4, confirm that the assumption works well. 

Comparison of theoretical (lines) and experimental results (symbols) for a system containing decyl dimethyl phosphine oxide as main component and dodecyl dimethyl phosphine oxide as... 

Fig. 6.13 shows the agreement between the elasticity modulus, derived form the adsorption isotherm and from relaxation experiments with n-dodecyl dimethyl phosphine oxide solutions. 

Fig. 6.13 Dilational elasticity modulus of n-dodecyl dimethyl phosphine oxide determined for oscillating bubble experiments ( ), and calculated from the adsorption isotherm ( ) according to Wantke etal.(1993)...

The adsorption kinetics of a surfactant to a freshly formed surface as well as the viscoelastic behaviour of surface layers have strong impact on foam formation, emulsification, detergency, painting, and other practical applications. The key factor that controls the adsorption kinetics is the diffusion transport of surfactant molecules from the bulk to the surface [184] whereas relaxation or repulsive interactions contribute particularly in the case of adsorption of proteins, ionic surfactants and surfactant mixtures [185-188], At liquid/liquid interface the adsorption kinetics is affected by surfactant transfer across the interface if the surfactant, such as dodecyl dimethyl phosphine oxide [189], is comparably soluble in both liquids. In addition, two-dimensional aggregation in an adsorption layer can happen when the molecular interaction between the adsorbed molecules is sufficiently large. This particular behaviour is intrinsic for synergistic mixtures, such as SDS and dodecanol (cf the theoretical treatment of this system in Chapters 2 and 3). The huge variety of models developed to describe the adsorption kinetics of surfactants and their mixtures, of relaxation processes induced by various types of perturbations, and a number of representative experimental examples is the subject of Chapter 4. 

Harmonic and transient relaxation experiments for dodecyl dimethyl phosphine oxide solutions were performed with the elastic ring method by Loglio [240]. This methods allows oscillation experiments in the frequency range from about 0.5 to 0.001 Hz and is suitable for comparatively slow relaxing systems. Slow oscillation experiments can be performed much easier now with the pendent drop apparatus [186]. Both techniques are also able to perform transient relaxation experiments. The two types of experiments have a characteristic frequency defined in the same way by Eq. (4.110). 

The easiest penetration experiments are those with a monolayer of an insoluble component spread on a subphase which contains a soluble component of the same homologous series. An example is the study by Fainerman et al. [115] of the penetration of the soluble dodecyl dimethyl phosphine oxide (C,2DMPO) into a monolayer of the insoluble eicosyl dimethyl phosphine oxide (CjqDMPO). The monolayer isotherm of C20DMPO at 20 °C shows a break... 

There are some informations about monotonous decrease of the equilibrium surface tension, dilatational elasticity, and adsorption of lysozyme for non-ionic surfactant decyl dimethyl phosphine oxide (Cj DMPO) as the concentration of surfactant increases in the mixture. However, in the case of mixtures of non-ionic surfactants with more flexible proteins like P-casein, the elasticity of the interfacial layer decreases before passing through a maximum as the concentration of surfactant increases [7], Possibly, the weaker interfacial network formed by P-casein as compared to globular proteins determines the dilatational response of the mixtures. The same picture was shown for the system P-casein mixed with dodecyl dimethyl phosphine oxide (C,2DMPO). For all studied frequencies (0.005-0.1 Hz) the elasticities for adsorption layers have a maximum about 4x10" mol/1 Cj2DMPO concentration. It was shown the obtained values are very close to those measured for the surfactant alone. Thus, in this concentration region the surfactant dominates the surface layer. In our case we have... 

Oscillation experiments with the elastic ring method in the frequency range from about 0.5 to 0.001 Hz for dodecyl dimethyl phosphine oxide solution were first conducted by Loglio [68]. 

The values of k , calculated from Eiquation 5.13, are almost independent of [CioE4]j. - However, the inhibition by dodecyl(dimethyl)phosphine oxide (C12PO) is less than that by C,oE4, for example, with 0.05 M CTABr and 0.05 M C12PO, W kobs = 4.83 sec as compared to 10 k bs = 3.0 sec with added 0.05 M C10E4, and rate differences are similar over a range of conditions. These qualitative observations indicate that the simple treatment with constant kM probably does not fit the effects of C,2PO. The simplest explanation of this failure is that the rate constant k increases on addition of C,2PO, and this increase is found to fit the following empirical equation ... 

An example of the amplitude- and phase-frequency characteristics of pressure oscillations inside a closed cell with excitation in the cell are presented in Fig. 8. The characteristics are obtained for parameters of the Langmuir isotherm and the diffusion eoefficient characteristic for the model surfactant dimethyl dodecyl phosphine oxide (E = 4.39-10 ° mol/cm, b = 1.7-10 cmVmol, D = 4-10 cm /s, [30]). The parameter co is here assumed to be negative. 

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