Mesophases in mixtures of water and polyoxyethylene surfactant: Variations of repeat spacing with temperature and composition

Abstract

Abstract." Lamellar (L~) and hexagonal (Hi) mesophases, formed in mixtures of water and polyethylene oxide (PEO) oleylethers (average EO-numbers 5 (a), 8.5 (b) and 14 (c)) and pure hexaoxyethylene dodecylether (d), were investigated with small-an~e X-ray diffraction. Analysis of repeat spacings shows a deviation from linear one-and two-dimensional swelling of L~ and P/l, respectively, when a transition to a mesophase with a larger curvature of the interface is approached. With regard to L~, in this respect similar behaviour is observed for a pure surfactant (d) and a surfactant with an EO-length distribution (b). It is proposed that, through the formation of aggregates of limited extent, water filled pores in the mesophases arise. This is confirmed by analysis of the intensity ratio of diffraction maxima of first and second order in L~. Models for finite aggregates are introduced. These consist of (1) lamellae, infinite in one direction and with variable length L in a direction perpendicular to the first, with cylindrical edges and (2) cylinders with variable length L bounded by spherical caps. According to these models, under certain conditions, finite aggregates may be formed without an increase of the interfadal area per surfactant molecule. Applying the models to the regions where non-linear swelling is observed, reasonable values for L are found, which decrease progressively when the phase transition is approached.

Changes of mesophase structure of BRIJ 96/water mixtures on addition of liquid paraffin

“…The isotropic phase, V1, that is often present in a small region between H 1 and L~ in similar systems [7], was not found. As we stated before [13], the difference is probably due to variations in the "quality" of the supplied commercial surfactants. (The simukaneous presence of two mesophases is disclosed by SAXD, see below.)…”

“…1. Instead, a region with mixed H1/L~ was observed [13]. The isotropic phase, V1, that is often present in a small region between H 1 and L~ in similar systems [7], was not found.…”

“…Recently, we reported on the repeat spacings observed with SAXD in H1 and L,~ of several polyoxyethylene oleylethers and hexaoxyethylene glycol dodecylether at various compositions and temperatures [13]. Here, we report on the effect of the addition of liquid paraffin on the mesophases formed in mixtures of water and BRIJ 96, a polyoxyethylene oleylether with a specified average number of 10 oxyethylene units per molecule.…”

“…Characterization of the batch of surfactant used showed that the average number of EO-units per molecule was 8.5 [13]. Characterization of the batch of surfactant used showed that the average number of EO-units per molecule was 8.5 [13].…”

Development of Topical Niosomal Gel of Benzoyl Peroxide

“…Analysis of data of drug leakage study by applying ANOVA reveals that niosomal drug gel is significantly more stable as compared niosomal suspension and also both formulations are significantly more stable at refrigerated temperature than room temperature, as it is observed in Figure 1. The reason behind higher leakage at higher temperature may be the higher fluidity of lipid bilayer at higher 11 temperature [11,12]. The stability of niosomes improved after incorporation into gel base may be due to prevention of fusion of niosomes.…”