The chapter describes the behavior of polymer-modified phospholipid-based w/o micro emulsions and its use for nanocrystal synthesis. We focused our interest on the naturally occurring crude soybean lecithin in presence of isooctane and water. In the case of the unmodified system an isotropic inverse micellar region can be observed in the oil corner. By adding an anionic polyelectrolyte, i.e., sodium polyacrylate, the area of the optically clear phase is drastically decreased. The incorporation of the neutral polymer poly(ethylene glycol) (PEG), and the cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC) induces the formation of an isotropic narrow phase channel in the area of the origin L_2 phase. The cationic poly(ethyleneimine) can be incorporated much better up to polymer concentrations of 5 wt%. From ~1H NMR self-diffusion experiments one can conclude that the isotropic phase is indeed a reverse micellar microemulsion. Rheological experiments show a non-Newtonian flow behavior of the microemulsions. By means of differential scanning calorimetry (DSC) bulk water can be detected in the reverse w/o droplets. In comparison to the natural soybean lecithin, a pure phosphatidylcholine (>95%), modified with sodium dodecylsulfate, and/or PDADMAC was investigated. The reverse microemulsion droplets were used as a template phase for the synthesis of BaSO_4 nanoparticles. The polymers involved in the redispersion process, influence the size, and supramolecular arrangement of the nanoparticle composites formed.
展开▼
