Dodecane dispersions

Figure 4.21 (A and B) Transmission electron micrographs and electron diffraction patterns recorded on tribologic film particles obtained in the presence of OCABS in a dodecane dispersion.(C, D) Corresponding EDX and EELS spectra. The film is composed of nanocrystallites of calcite (diffraction) with an average size of 10 nm aggregated by means of ill-ordered areas (diffuse diffraction). The EDX spectrum reveals that iron is not detected. The EEL spectrum at the carbon K-edge points out that no more hydrocarbon chains are present in the film...

Water-borne polyurethane coatings are formulated by incorporating ionic groups into the polymer backbone. These ionomers are dispersed in water through neutrali2ation. The experimental 1,12-dodecane diisocyanate (C12DI Du Pont) is especially well suited for the formation of water-borne polyurethanes because of its hydrophobicity (39). Cationomers are formed from IPDI, /V-methyIdiethan olamine, and poly(tetramethylene adipate diol)... 

Stopped flow mixing of organic and aqueous phases is an excellent way to produce dispersion within a few milliseconds. The specific interfacial area of the dispersion can become as high as 700 cm and the interfacial reaction in the dispersed system can be measured by a photodiode array spectrophotometer. A drawback of this method is the limitation of a measurable time, although it depends on the viscosity. After 200 ms, the dispersion system starts to separate, even in a rather viscous solvent like a dodecane. Therefore, rather fast interfacial reactions such as diffusion-rate-limiting reactions are preferable systems to be measured. 

A typical example is the protonation of tetraphenylporphirin (TPP) at the dodecane-acid solution interface. The interfacial protonation rate was measured by a two-phase stop flow method [6] and a CLM method [9]. In the former method, the stagnant layer of 1.4 jxm still existed under the highly dispersed system. In the CLM method, the liquid membrane phase of 50-100 /am thickness behaved as a stagnant layer where the TPP molecule has to migrate according to its self-diffusion rate. 

Initial studies were made with the Rank Bros, electrophoresis unit, using the dilute supernatant suspension over a dispersion of 3.33g of carbon black per liter of dodecane equilibrated for 24 hours with the added 0L0A-1200. The electrophoretic mobility (u) of 1-3 pm clumps of particles was observed at a field of 100 volts per centimeter. The zeta-potentials ( ) were calculated... 

Figure 8. Conductivity of stirred 10% suspensions of carbon black in dodecane with OLOA-1200 dispersant. Triangles- 5 minutes after dispersant added circles- 45 minutes after addition and squares- 12 hours after addition. Reproduced with permission from Ref. (16). Copyright 1983, Elsevier Science Publishers.

FIGURE 7.19 Small-angle X-ray scattering spectra of solutions of [DMDOHEMA] = 0.7 M in various solvents (x) extractant reverse micelles in dodecane or extractant dispersed in structured solvent (A) for dodecane octanoi= 24/76 and (O) octanol. (From F. Testard, P. Bauduin, L. Martinet, B. Abecassis, L. Berthon, and C. Madic, Radiochim. Acta, 96 1-8, 2008. With permission.)... 

From macroscopic observations, it appears that in the DMDBTDMA-dodecane system the nature of the third phase (liquid, gel, or solid) (140) depends to a large extent on the extracted species. In some cases, microphase separations can be obtained, that is, the coexistence of a more crystalline phase with domains of diluted phase that do not separate upon centrifugation. In classical colloidal literature (141), this situation is described as a dispersion of tactoids in the form of small amounts of liquid crystals, giving macroscopically a gel. 

M 54] [P 49] A validation of the volume-tracking method, applied for droplet simulation, was performed by comparing the simulated equivalent diameters of droplets with data derived from analytical correlations [135], Assuming a nozzle diameter of 1 mm and taking water and dodecane as dispersing and continuous... 

The artificial membranes are prepared by dispersing a 20% (w/v) dodecane solution of a lecithin mixture (PN 110669 pION, USA) on a microfilter disc (125 /xm thick, 0.45 /urn pores). The system mounted is adequately stirred to properly simulate in vivo situations, that is, to obtain the expected unstirred water layer (UWL) of 30-100 /urn thickness [48]. 

While examining time-dependent phenomena of silver bromide particles, we made many repeat measurements. With care, standard deviations could be kept below 1%. Figure 6, for instance, contains the diameters calculated from the peak maxima for 44 injections of a silver bromide dispersion. Four consecutive injections were made into the same dodecane-protected spin fluid, so that experiments in 10 different spin fluid gradients are represented here. Monitoring of the spin fluid temperature was required, since this variable affects both density and viscosity. Corrections were also made for the volume change of the spin fluid caused by successive injections Cl, 3). 

The premixed emulsion is comprised of salted water droplets dispersed in a 1 9 mixture (w/w) of dodecane and a lipophilic surfactant (Admul wol 1403) The... 

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