Self-Assembled Liquid Particles: How to Modulate their Internal Structure - Food Colloids: Self-Assembly and Material Science - page 72

only 20.3 wt.% water. As soon as the water solubilization capacity is exceeded,
i.e., when the composition reaches the excess water region, the lattice param-
eters for the distinct symmetries coincide within experimental error: 12 above
this point any additional water is then expelled from the mesophase (excess
water). At 581C, the inverse hexagonal phase can solubilize almost 23.8 wt.%
water, as compared with just 21.3 wt.% at 871C. Consequently, the lattice
parameter of this mesophase (in the excess water) decreases from 5.54 to 5.10
nm. Thus, there exists a temperature-induced shrinking in the samples in excess
water. This is important, since the most interesting of the bulk samples is the
one that is already in equilibrium at room temperature with excess water
(prepared with 40 wt.% water, for example), because this is the sample that can
be best compared to the aqueous dispersions. In these bulk samples in excess of
water, increasing temperature induces a phase transition from cubic Pn3m via
H 2 to L 2 , while greater amounts of water are expelled; for instance, from 20 to
941C, 38% of the initial water content is expelled.
To produce an MLO + water system in its colloidal emulsified state, the
MLO was dispersed in large amount of excess water by means of ultrasoni-
cation, using the Pluronic copolymer F127 as stabilizer. This led to the
formation of sub-micrometre-sized particles with self-assembly structured
interiors, which could be observed by cryo-TEM (Figure 2). Figure 3 shows
the scattering curves of the dispersions (thin lines) and the corresponding
nondispersed bulk phase in excess water (thick lines) at three different temper-
atures (25, 60, and 981C). The resemblance of the corresponding scattering
curves at each temperature is remarkable: the peak positions for bulk systems
and dispersions practically coincide. The peaks of the dispersions are only
broadened and lowered in the scattered intensity. At the same positions as in
the bulk, we observe six peaks in the emulsified cubic phase (ECP) and three
peaks in the emulsified hexagonal phase (EHP). This quantitative agreement
between the structural parameters measured in the dispersed particles and the
nondispersed bulk in excess water clearly demonstrates that the confined
100 nm
Figure 2 Cryo-TEM image of a dispersion consisting of 4.625 wt.% MLO, 0.375 wt.%
F127, and 95 wt.% water. Cubosomes coexist with vesicles at 251C