Brij 92/96 mixtures

Figure 2.19 Phase diagrams of dodecane-water-Brij 92/96 mixtures. 0,W,S = 100% oil, water, surfactant, respectively. HLB values of the surfactant mixtures are shown to the right of each diagram. Phase boundaries for Li, L2, G, and M2 phases shown. Other symbols represent 2L, two-phase oil-water system (emulsions of varying stability) M, microemulsion I, isotropic elastic I +, isotropic elastic + disperse oil phase. Filled black regions stable emulsion zones. From Lo et al. [37] with permission.

Figure 2.20 Water uptake into non-aqueous L2 dodecane phase as a function of the calculated HLB of Brij 92/96 mixtures. The dodecane results obtained at O 25 %, A 40 % and 50% w/w surfactant levels. From Lo et al. [37] with permission.

Evidence of decreased solubility of both chlorhexidine diacetate and chlor-hexidine dihydrochloride in Brij surfactant mixtures has been adduced [203] though this is only clear in the case of the dihydrochloride at concentrations higher than 5% when uptake is some 30% higher in Brij 96 than in Brij 92-96 mixtures if HLB =11. 

Some tabulated results are given below comparing the effects of y-irradiation on the viscosity of PEG 6000 and Triton X-100 (Table 11.11) and Triton X-405, cetomacrogol 1000 and a Brij 92-96 mixture (Table 11.12). Surface tension concentration plots for Triton X-100 before and after irradiation are shown in Fig. 11.24. 

Phenylene-bridged periodic mesoporous organosilicas, with both amorphous and crystal-like walls, (referred to in the following as AW-Ph-HMM and CW-Ph-HMM, respectively) were synthesized and characterized as previously reported [6,7]. BTEB was used as a precursor for both solids the surfactant was Brij-76 (Ci8H37(OCH2CH2)nOH) in acidic media for AW-Ph-HMM and octadecyl-trimethylammonium bromide(ODTMA) in basic media for CW-Ph-HMM. A purely siliceous MCM-41 sample was also synthesised, the first step being the solution of octadecyltrimethylammonium bromide in a basic aqueous solution (NH3), kept a 333 K. Tetraethyl orthosilicate (TEOS) was then added in all cases dropwise, and the mixture stirred for 24h at room temperature (H20 34.2 g/ NH3 (15%) 8.52 g/ ODTMA 0.73 g TEOS 3.24 g). After further 24 hours in hydrothermal conditions at 368 K, the sample... 

The AE blend Brij 35 with the general formula CnH2n+i 0(CH2CH20)mH was analysed by MALDI MS prior to use for biochemistry research. Separation results of thin-layer (TLC) and RP-LC of these surfactants were compared [30]. Brij 35, as a mixture of Ci2 and C14 homologues (to = 15-39), was detected qualitatively as [M + Na]+ and [M + K]+ ions and quantitatively after TLC and RP-LC separation. 

Systems and materials. The reaction was carried out at several compositions in an ionic and in a nonionic system. The ionic system consisted of an emulsifier (49.6 wt % cetyltrimethyl ammonium bromide (CTAB)/50.4% n-butanol), hexadecane, and water. The nonionic emulsifier consisted of 65.7% polyoxyethylene (10) oleyl ether (Brij 96) and 34.4% n-butanol, again with hexadecane and water. In both systems, mlcroemulslon (pE) compositions used were obtained by diluting an initial 90 weight percent (%) emulsifler/10% oil mixture with varying amounts of water. Micro-emulsion samples thus obtained had final compositions of 30 to 80% water. Phase maps describing these systems have been published (10-11). 

Effect of Ionic Strength. Both yE systems were examined for ionic strength effects. Microemulsion compositions were prepared at 70% water, with a cyanide concentration of 0.032 M with respect to the water content. Potassium bromide was used to vary the ionic strength of the reaction mixtures. Ionic strength in the CTAB yE was varied from 0.04 to 0.34. Since the Brij yE tolerated a much higher salt concentration without phase separation, ionic strength in that system was varied between 0.04 and 1.80. As will be seen, the Brij system exhibits a salt effect, while the CTAB yE does not. Rate constants obtained for reaction (1) in the Brij yE were therefore corrected to take into account the effect of ionic strength in that system (vide infra). 

In contrast to the R-preference displayed by CALB, quite impressive S-preference toward several 1-aryl-l-ethanols can be achieved by using a protease, the commercially available subtilisin Carlsberg, as catalyst, and isopropenyl pen-tanoate as the acyl donor in THF in the presence of sodium carbonate [74]. To achieve a successful resolution, the protease has to be treated with a mixture of two surfactants, octyl-P-D-glycopyranoside and Brij 56 [the monocetyl ether of polyoxyethylene (10)], 4/1/1 by weight, at pH 7.2, and then lyophilized before use. 

Fig. 11. Relative phase volume-corrected rate constants vs weight fraction water for the io-dosobenzoate-catalysed hydrolysis of a phosphate ester in water/hexadecane microemulsions stabilized by various surfactant/cosurfactant mixtures. Curve (a) Brij 96/1-butanol curve (b) CTAB/I-butanol curve (c) CTAC/dibutylformamide curve (d) CTAB/2-methylpyrrolidone and Adogen 464 (from [26])...

Ghosh and co-workers have shown in several studies that Brij 35 and Pol 10 in water provide suitable environments for the photochemically induced reductive dechlorination of chlorobiphenyls [75,77,82,83]. Ghosh and Sayler have demonstrated that photochemistry and microbes work symbiotically to degrade PCB mixtures [76,80]. Photochemistry in a surfactant/water solution converts highly chlorinated biphenyls into much less chlorinated ones. The microbes, which do not oxidize the highly chlorinated biphenyls, then oxidize the less chlorinated biphenyls. For a related study on the combined degradation of a PCB mixture and microbes see [88]. 

Microcrystalline cellulose (Merck) appears to have been used most successfullybut even this support matrix should be used with continuous mixing to maintain adequate suspension. The inclusion of a nonionic detergent in the incubation mixture (0.5% v/v Tween-20 - 0.1% v/v Brij-35 ) helps to keep the particles dispersed and to reduce nonspecific binding. Other aproaches and matrices used with variable success have included conjugation to iron oxide particles coated with polymerized w-diaminobenzene, adsorption to individual polystyrene balls 6.4 mm in diameter, and adsorption to polystyrene plastic tubes. 

Highly ordered lamellar gel microstructures are formed by certain surfactants and mixtures of a surfactant and long-chain fatty alcohols in water. Using small angle X-ray scattering (SAXS), an ordered lamellar stack lattice model was proposed for the gel formed by 10% w/w cetostearyl alcohol containing 0.5% cetri-mide surfactant. In contrast, the microstructure of a Brij 96 gel depends on the surfactants concentration. A hexagonal liquid-crystalline gel structure was... 

Figure 7.13 Variation of mean globule size in a mineral oil-in-water emulsion as a function of the HLB of the surfactant mixtures present at a level of 2.5%. Surfactants Brij 92-Brij 96 mixtures.

Figure 7.14 The change in critical HLB values as a function of added salt concentration, where the salt is either NaCl or Nal. Results were obtained from measurements of particle size, stability, viscosity and emulsion type as a function of HLB for liquid paraffin-in-water emulsions stabilised by Brij 92-Brij 96 mixtures. Data from different experiments showed different critical values hence, on each diagram hatching represents the critical regions while data points actually recorded are shown. Results in (a) show particle size and stability data those in (b) show the HLB at transition from pseudoplastic to Newtonian flow properties (see section 7.3.10) and emulsion type (o/w— w/o) transitions.

Figure 2. Cloud point curves of Brij 52/Brij 30 80/20 mixture with a water/surfactant ratio of 5.0, acrylamide/surfactant ratio of 1.0, total dispersed-phase volume fraction of 0.136, and seven continuous- phase ethane concentrations (weight %). ...

Effect of Pressure on Apparent Micelle Size. The pressure-induced color changes that are observed in the one-phase region of the Brij-based microemulsion systems suggest that the size of the organized assemblies in the ethane/propane mixtures is changing as the pressure is changed. Initial considerations of dynamic light... 

Investigation of the phase behavior of the Brij-based microemulsion system in ethane/propane mixtures defines the operating conditions for the polymerization process and provides evidence of formation of stable microemulsions in supercritical... 

In these studies, the system water/Brij 30 (polyoxyethylene lauryl ether with an average of 4mol ethylene oxide/decane) was chosen as a model to obtain O/W emulsions. The results showed that nanoemulsions with droplet sizes on the order of 50 nm were formed only when water was added to mixtures of surfactant and oil (method B), whereby an inversion from a W/O emulsion to an O/W nanoemulsion occurred. 

Figure 14.1 Schematic representation of the experimental path in two emulsification methods. Method A. addition of decane to water/surfactant mixture Method B. addition of water to decane/Brij 30 solutions.

HLB values of the surfactants 6a-c, f, g and llg have also been evaluated experimentally by using the required HLB concept of the oil/water system [40]. The HLB system predicts the optimum emulsion stability when the HLB value of the surfactant systems matches the required HLB of the oil/water system. The required HLB is the value at which enhanced emulsion stability will be attained. Optimization of the performance can be achieved by only including surfactant systems with similar HLB values. Mixtures composed of a mannuronate-type surfactant and a commercial cosurfactant with a known HLB value (Span 85, Brij 72, Span 40, Span 20) were formulated with various surfactant/cosurfactant ratios (20, 40, 60, and 80 wt%) to create different HLB values of the system. Then, the performance was determined and plotted vs the HLB. A maximum appears in the plot and the... 

Cyclophosphazenic polypodands. Obtained as a mixture from the commercial Brij 30, these cheap and efficient catalysts are comparable to most of the common phase-transfer catalysts. 

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