Sponge phase structure

The effect of shear on the L3 phase in the cetylpyridinium chloride/hexanol/(water+NaCl) system with a significant amount of added dextrose has been examined. Additions of of dextrose slow down the diffusional process discussed above. At low shear rate, the sponge phase structure is retained but starting at a shear rate above 500 s, shear thinning reveals the occurrence of a transition to a lamellar phase. Unfortu-... 

The oilseed reaches typically 112.8°C (235°F), as read by a thermometer near the die plate, and approximately 10-13% moisture. Internal pressure is 13 0 times greater than atmospheric pressure. At this pressure and temperature, all moisture, even injected steam, is compressed into the liquid phase. On release into atmospheric pressure, some of the moisture flashes to reach equilibria. This vaporizing moisture inflates the collets with internal pores and surface cracks, imparting a porous, sponge-like structure to the collet. 

The oilseed reaches 235°E at 10-13% moisture at the die plate under a pressure of 30 0 atmospheres. All the water (natural moisture, injected steam, and liquid water) is compressed into the liquid phase. When the product leaves the high-pressure interior of the expander, some of the moisture flashes to reach equilibrium at atmospheric pressure. The flashing inflates the collets with internal pores and surface cracks, giving the collets a sponge-like structure. Eigure 17 shows typical soybean collets made with expander for solvent extraction. 

Phase-inversion membranes frequently show a sponge-like structure. The volume flux through these membranes is described by the Hagen-Poiseulle or the Kozeny-Carman relation, although the morphology is completely different. 

While MCM-41- and 48-based materials dominate as the primary mesoporous materials explored for gas-phase propylene epoxidation, a recent article examines the reactivity of Au deposited on Ti-TUD containing 3 mol% Ti [57]. Ti-TUD consists of a sponge-like structure with an average pore size of about 13 run. Although the specific surface area of this material is less than that of MCM-41 or MCM-48, the larger pore system allowed for essentially all of the deposited Au to have access to the pore system. A maximum rate of 53.7 gpo kgcat 470 °C... 

This is the usual type of HPLC stationary phase. These materials are 1.8, 3.0, 3.5, 5.0 or 10 gm in size. As a rule of thumb, their performance, i.e. the plate number per unit length, doubles each time from 10 to 5 and 3 gm, whereas the pressure drop increases each time by a factor of four. Their internal structure is fully porous and can best be compared with the appearance of a sponge (however, in contrast to a sponge, the structure is very rigid). Within the pores the mobile phase (and the analytes) does not flow but moves only by diffusion. 

Based on benzene extraction of the NR from the samples, SEM of the remainder allowed the authors to conclude that the EVAc forms the dispersed phase when its proportion is <40% and that NR forms the dispersed phase when its proportion is <40%. In the NR/EVAc, 60/40 and 50/50 blends, both the polymers remain as continuous phases leading to a sponge-Uke structure for the blend. 

In preparing membranes via the phase inversion process for applications in pressure-driven processes, the formation of macrovoids should be avoided completely. These finger-like pores of the type present in the substructure of membranes (b) and (c) of Fig. 3.6-1, severely Hmit the compaction resistance of the membrane. Membranes with a sponge-Hke structure (Fig. 3.6-la) are to be preferred. 

The condensation of vapors inside nanometric PSi structures has been investigated (Moretti et ah, 2007). The liquid phase covers the pore surface as a thin film and fills a volume fraction in the sponge-like structure depending on the physical and chemical properties of each compound. The filling factor of different substances can be measured as a function of fractal-like PSi film porosity by means of an interferometric technique. The capillary condensation exhibits a nonlinear behavior at high porosities (greater than 0.8). 

One approach to the study of dual phase continuity in sequential IPN s is through the decross linking and subsequent dissolving out of one polymer or the other. For example, in a recent study of a polypropylene/EPM morphology, the ethylene-propylene rubber component was dissolved out, leaving a sponge-like structure of polypropylene, as observed via scanning electron microscopy. 

The structures of the phases L4, La, and L3 were characterized by means of several techniques and confirmed by freeze-fracture electron microscopy [47,79,86-88]. Typical electron micrographs showing the organization of the bilayers in phases L3 and L4 are shown in Fig. 5. These clearly show the continuity of the bi layer in the sponge phases and the existence... 

Anderson and Wennerstrom [33] calculated the geometrical obstruction factors of the self-diffusion of surfactant and solvent molecules in ordered bicontinuous microstructures, which serve as good approximations also for the disordered bicontinuous microemulsions and L3 (sponge) phases. The geometrical obstruction factor is defined as the relative diffusion coefficient DIDq, where D is the diffusion coefficient in the structured surfactant system and Z)q is the diffusion coefficient in the pure solvent. In a bicontinuous microemulsion the geometrical obstruction factor depends on the water/oil ratio. An expansion around the balanced (equal volumes of water and oil) state gives, to leading order. 

The diffusion behavior implies a rapid, but continuous, change in structure from discrete oil droplets to bicontinuous to discrete water droplets with increasing temperature. The bicontinuous structure appears to be well described by the constant mean curvature surface structures of low mean curvature rather than a tubular structure. The same applies to the bilayer phases, often denoted L3, L4, or sponge phases, also included in Fig. 6. 

The effect of adding various lipids to monoolein was discussed above. These lipids are soluble in either water (bile salt) or oil (triglyceride) or hardly soluble at all (lecithin). If a substance that is soluble in both water and oil, e.g., propylene glycol, is added to the monoolein-water system, the cubic liquid crystal undergoes a transition to a sponge or L3 phase [13], as shown in Fig. 5. The structure of the sponge phase has been described as a melted bicontinuous cubic phase [14]. 

Other nonionic surfactants, that is, GMO, formed unique structures upon addition of ethanol or Transcutol. The unique isotropic fluid Ql phase formed in the GMO/ethanol/water mixture and is surmised to be a transition phase between the cubic bicontinuous phase and the sponge phase. 

As we will see below, bicontinuous structures are very significant in many contexts of amphiphile self-assembly. Another type of bicontinuous structure in simple surfactant-water solutions is the sponge phase , formed also in quite dilute surfactant solutions (Figure 19.26). This structure forms for all classes of surfactants but in particular for nonionics. We will also mention that the structure of the sponge phase is related to that of many microemulsions. 

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