New Lyotropic Complex Fluid Structured in Sheets of Ellipsoidal Micelles Solubilizing Fragrance Oils

Abstract

New lyotropic, fragranced, viscoelastic fluid with a complex structure is obtained from fragranced microemulsions by the addition of a fatty acid. Nonhomogeneous mixing of an appropriate nonionic surfactant, a fatty acid, and a fragrance oil led to the formation of anisotropically shaped and highly oriented micelles in aqueous solution. The nano- and microstructures, and consequently the viscosity, are controlled by the balance of fatty acids used as a cosurfactant and fragrance molecules, which partly behave as a cosurfactant and partly segregate in the micelles of the hydrophilic nonionic surfactant. The transition from isotropic microemulsion to a more structured viscoelastic solution is characterized by X-ray scattering and rheological methods. Considering our X-ray scattering results, we propose a structure composed of planar sheets of ellipsoidal micelles arranged in a lamellar type of stacking. The complex structured, low viscous, transparent fluid is capable of solubilizing a fragrance inside the ellipsoidal micelles, as well as retaining microparticles containing fragrance, without the addition of a polymeric thickener or another gelator. These features allow the creation of a 2-in-1 fragrance-solubilizing liquid product compatible with all types of home and body care consumer products.

Figure 1

Chemical structure of the fragrance oils used for sample preparation: (A) dihydromyrcenol and (B) exaltolide.

Figure 2

Graphical representation of the integration process.

Figure 3

(A) 2D SAXS images for the LA concentration increase samples. (B) Radial integrations on the 2D images for the LA concentration increase series. Symbols: experimental points. Continuous lines: model fits. The sample-to-detector distance for this data was 0.8 m.

Figure 4

(A) Radial profiles of the scattered intensity of samples at different lauric acid concentrations. The concentration of fragrance (dihydromyrcenol) and surfactant is constant and equal to 1.9 and 6% wt, respectively. (B) Radial profiles of the scattered intensity of samples at different fragrance (DHM) concentrations. The concentration of lauric acid and surfactant is constant and equal to 1.6 and 6% wt, respectively. In all curves, symbols: experimental data, solid lines: model fits. Labels H and V stand for horizontal and vertical directions, respectively. The sample-to-detector distance for this data was 0.8 m.

Figure 5

Sketch of the structure proposed based on the X-ray diffraction results: (A) with oblate ellipsoidal micelles and (B) with prolate ellipsoidal micelles.

Figure 6

(A) 2D SAXS images for the DHM concentration increase samples. (B) Radial integrations on the 2D images for the DHM concentration increase series. Symbols: experimental points. Continuous lines: model fits. Sample-to-detector distance for this data was 0.8 m.

Figure 7

SAXS data for sample solubilizing exaltolide (E1). (A) 2D SAXS images. (B) Radial integrations on the 2D images. (C) Radial profiles of scattered intensity (CH—horizontal cut; CV—vertical cut). Symbols: experimental data, solid lines: model fits. Sample composition: 89.5% wt (water + propylene glycol) + 6.0% wt C_9–11E₈ + 1, 6% wt lauric acid + 2.9% wt exaltolide. The data obtained at 8.0 m (USAXS) was combined with the curve at 0.8 m (SAXS).

Figure 8

Isotropic-to-birefringent phase transition on a dilution line (samples Q0–Q6). The active matter content in % wt is written on the images. The sample tubes with an inner diameter of 20.4 mm were photographed through crossed polarizing filters. The scale is 5 mm.

Figure 9

(A) 2D SAXS images for the dilution series samples. For sample Q6, the diffraction peak was behind the beam-stopper for the SAXS configuration; therefore, the USAXS data was used (Q6U). One observed variation on the USAXS 2D image; so, the first collected frame (Q6U₇₇₃) and the last collected frame (Q6U₇₈₀) are shown. (B) Radial integrations on the 2D images SAXS for the dilution line series. (C) USAXS data. Symbols: experimental points. Continuous lines: model fits. For samples Q0–Q6, the sample-to-detector distance was 0.8 m. For sample Q6U, the sample-to-detector distance was 8.0 m.

Figure 10

(A) Radial profiles of the scattered intensity of samples containing different concentrations of active matter along a dilution line: 60% wt (black), 33% wt (red), 25% wt (green), 19% wt (magenta), 12.5% wt (blue), 9,1% wt (orange), and 5.6% wt (dark gray). For samples Q0–Q6, the sample-to-detector distance was 0.8 m. For sample Q6U, the sample-to-detector distance was 8.0 m. (B) Repeat distance as a function of active matter volume fraction. The red line represents the linear fit of the experimental points. The slope is 1.18, and d₀ calculated from the intercept is equal to 23.6 Å.

Figure 11

FTIR spectra of single-component ingredients used in the studied samples: Neodol (blue), lauric acid (red), dihydromyrcenol (green), and their mixture (black) in the ratios used in the sample L3: Neodol/DHM = 0.94 and Neodol/LA = 1.43.

Figure 12

FTIR spectra of mixtures of Neodol, dihydromyrcenol (DHM), and LA at different concentrations of LA. The ratios (Neodol + DHM) to LA correspond to the ratios in the samples L0–L4.

Figure 13

(A) Flow viscosity behavior of samples as a function of lauric acid concentration. (B) Oscillatory behavior of samples as a function of lauric acid concentration. (C) Dispersion of polymeric microcapsules in a microemulsion (left) and in a gel-like (right) formulation from the present study. Creaming of the microcapsules in the microemulsion is observed under storage at room temperature. (D) Microscopic image in a transmitted light of the complex viscoelastic fluid with dispersed microcapsules (black circles). The microscopy clearly shows the internal structure of the complex material.

Figure 14

Flow (A) and oscillatory (B) behavior of samples from the dilution line.

Figure 15

Oscillatory curves of gels containing (A) dihydromyrcenol and (B) exaltolide.