Four different one-phase regions: two liquid phases (L and L3) and two liquid crystalline phases (Lα and V2)
of the MO/NMP/water system, were studied by SAXS, PGSE-NMR, and rheology at 20 °C. The location of
the dramatic increase in solubility of MO, in binary NMP/water mixtures, can be explained in terms of the
presence or absence of free water, as a consequence of strong NMP(water)2 complex formation in the binary
NMP/water system. A direct effect of this complexation is aggregate formation at a certain region within the
L phase. The microstructure of the L3 phase can be modeled as bicontinuous according to the theory of
interconnected rods when formation of NMP(water)2 complexes are taken into consideration. The swelling
of the sponge phase correlates well to predicted swelling laws and characteristic lengths, as found in other
sponge phases. The cubic phase region of the ternary system consists of at least two different cubic phases,
with
and
symmetry of the space group, respectively. At higher NMP contents it seems as if the
symmetry of the space group transforms into
.
The phase behaviors of the subsystems of the ethyl acetate (EtAc)/monoolein/polyethylene glycol-poly(D,L-lactide-co-glycolide) (PLG)/water system have been determined. EtAc simultaneously solves MO and PLG in a liquid phase, denoted L. Lipid/polymer composite particles have here been formed by emulsification of such an L phase into aqueous solutions. Characterization, by means of confocal laser scanning microscopy, revealed that distinctive lipid domains appear inside the particles. In aqueous solutions, these lipid domains swell and finally leave the concentrated polymer matrix. The system exhibits a suitable phase behavior in order to form lipid/polymer composite particles. These composite particles may be interesting for drug delivery applications.
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