Preparation temperature, microemulsion stability

Qutubuddin and coworkers [43,44] were the first to report on the preparation of solid porous materials by polymerization of styrene in Winsor I, II, and III microemulsions stabilized by an anionic surfactant (SDS) and 2-pentanol or by nonionic surfactants. The porosity of materials obtained in the middle phase was greater than that obtained with either oil-continuous or water-continuous microemulsions. This is related to the structure of middle-phase microemulsions, which consist of oily and aqueous bicontinuous interconnected domains. A major difficulty encountered during the thermal polymerization was phase separation. A solid, opaque polymer was obtained in the middle with excess phases at the top (essentially 2-pentanol) and bottom (94% water). The nature of the surfactant had a profound effect on the mechanical properties of polymers. The polymers formed from nonionic microemulsions were ductile and nonconductive and exhibited a glass transition temperature lower than that of normal polystyrene. The polymers formed from anionic microemulsions were brittle and conductive and exhibited a higher Tj,. This was attributed to strong ionic interactions between polystyrene and SDS. 

First, it is apparent that the density of the ethane/propane continuous phase, rather than the molecular coxtqposition, determines the stability of the microemulsion. Stable microemulsions can be prepared in mixtures of ethane and propane over the entire concentration range. This allows examination of the effect of continuous-phase density on reaction rate, etc., while temperature and pressure remain constant. 

Barium hexaaluminate (BHA) has been prepared by a reverse microemulsion-mediated sol-gel method " . Several important preparation parameters were investigated in this work. Nanoparticles with excellent thermal stability could be obtained under optimal preparation conditions when compared to conventional sol-gel derived materials. This stability improvement is believed to occur since crystallization to the desired hexaaluminate phase took place at a relatively low temperature. Furthermore, this material has been tested as a catalyst for methane combustion . The light-olf temperature for 1 vol.% CH4 in air when using pure BHA as catalyst was observed to be 590 °C. This temperature could be lowered to 400 °C by depositing Ce02 on the catalyst. 

The formation of silver (Ag) nanoparticles in the rapid expansion of PFPE-NH4-stabilized aqueous AgN03-in-C02 microemulsion into a room-temperature reductant solution has been reported (9). In order to use Ag as a reference in this study, the same preparation of Ag nanoparticles via RESOLV was repeated. 

The applications of ILs are broadening with the advent of IL-based microemulsions. The IL-based nonaqueous microemulsions, particularly the IL/O ternary systems, have been considerably studied and subsequently used in industries. This class of mieroemulsion systems offers several advantages over the corresponding water-in-oil systems, due to the tunable size of the polar droplets, their wide range of temperature stability, and the ease of preparation for specific tasks. 

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