Self-Assembled Liquid Particles: How to Modulate their Internal Structure - Food Colloids: Self-Assembly and Material Science - page 81

100

EME
Hexosomes
Micellar Cubosomes
Cubosomes

80

60

40

20

0

50 60 70 80 90 100

δ

Figure 11 Temperature- d phase diagram of R -(+)-limonene-loaded Dimodan-based
dispersions (4.625 wt.% Dimodan U + oil, 0.375 wt.% F127, 95.0 wt.%
water). Dimodan U and MLO contain 59.5% and 86.1% MLO, respectively

explained in terms of an increase of the negative mean curvature of the
interface. The oil is a hydrophobic molecule that is not surface-active, and it
is located around the fatty tails of the monoglycerides and not at the oil-water
interfaces. Thus, the oil increases the hydrophobic volume of the chains
compared to their head group area. The presence of oil will then tend to bend
the interfaces towards a higher negative mean curvature, favouring the forma-
tion of spherical micelles. Nevertheless, this cannot be a sufficient condition to
explain why we can obtain the MCP phase rather than an L 2 , as many systems
just show a direct transition from inverse hexagonal to L 2 .
Figure 12 shows SAXS curves from R- (+)-limonene+Dimodan U disper-
sions stabilized by F127 at d ¼ 77. By decreasing the temperature from 90 to
11C, we show not only a transformation from EME to micellar cubosomes at
451C, but also a transition from Fd3m cubosomes to hexosomes at a rather low
temperature (151C). The latter transition happens over a broad temperature
range (35-151C) as can be seen from the first appearance of the (100) hexagonal
peak at q 1.3 nm 1 at 301C and the vanishing of the last contribution of the

MCP signal at 151C. As can be seen in Figure 11, the transition line between the
inverse hexagonal H 2 and MCP seems to be nearly vertical above 201C. But it
appears that below this temperature all transition lines are strongly tilted so
that the phases are shifted to lower d values. This enables the system to display
an indirect transition from H 2 to L 2 via MCP upon varying the temperature.
Nevertheless, even if this indirect transformation becomes possible by increas-
ing either the oil content or the temperature, it is available only over a narrow
range of oil content (22-27%). It is also interesting to note that, in all the

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