Microemulsion glasses

The principal motivation for studying these sugar-based microemulsion glasses came from the observation that water-oil-surfactant mixtures are extensively for nanomaterials synthesis with the central idea of switching dynamic self-assembly into chemically and mechanically stable supramolecular materials. Template polymerisations are classified as synergistic or transcriptive templating depending on whether the template itself participates in the reaction. 

However, an unavoidable complication of this approach to forming microemulsion glasses is the trapping of compositional gradients during the dehydration process. This is evident sometimes in the SANS spectra of the microemulsion glasses, which do not always follow the Teubner-Strey type scattering from bicontinuous microemulsions. Such... 

Figure 7.12 Spontaneous formation of a microemulsion glass. Sugar and surfactant powder dried to 99.5% dryness dispersed in oil at room temperature dissolves upon heating to 365 K to form a one-phase molten microemulsion glass. Gradual cooling of the molten glass to room temperature yields a solid microemulsion glass containing 52 vol.% liquid oil with a Mohs hardness of 0.7. (Reproduced from Dave et al. [97].)...

Uses Surfactant for hard-surf, floor cleaners, solvent-based degreasers, single phase microemulsions, glass and floor cleaners Features Good detergency and gloss retention... 

Agatonovic-Kustrin S, Glass BD, Wisch MH, Alany RG. Prediction of a stable microemulsion formulation for the oral delivery of a combination of antitubercu-lar drugs using ANN technology. Pharm Res 2003 20 1760-5. 

A number of matrices have also been used for the preparation of semiconductor nanoparticles, whereby the particulate material is grown within and subsequently fills the cavities of the host material. These includes zeolites,361 glasses,362 and molecular sieves,363-365 and can be viewed as nanochambers which limit the size to which crystallites can grow. Other synthetic methods include micelles/microemulsions,366-369 sol-gels,370,371 polymers,372-377 and layered solids.378... 

The cleaning composition may be used in concentrated or diluted form for cleaning soil from glass and metal parts, among others. This microemulsion shows that, by combining water and oil, metal surfaces can be cleaned effectively. This becomes possible because both oil- and water-soluble dirt is removed by the microemulsion. 

Microemulsions. Systems comprising microwater droplets suspended in an scCO T oil phase can be achieved with the use of appropriate surfactants, of which the best appear to be fluorinated. Microemulsions in supercritical hydrofluoro carbons are also possible. Potential may also exist for speciality coatings via low concentration solutions of fluorinated products in supercritical fluid for, e.g., thin-fitm deposition, conformal coatings, and release coatings. Supercritical CO2 will dissolve in formulated systems to improve flow and plasticize melt-processable materials to improve melt-flow characteristics and lower the glass transition temperature. 

Studies of inorganic photochemistry in unusual environments has attracted considerable attention. Photochemical studies conducted in organized assemblies such as micelles, microemulsions and vesicles,217 on surfaces such as porous Vycor glass,218 in a lamellar solid,219 and in the gas phase have been reported.220... 

This chapter concentrates on the results of DS study of the structure, dynamics, and macroscopic behavior of complex materials. First, we present an introduction to the basic concepts of dielectric polarization in static and time-dependent fields, before the dielectric spectroscopy technique itself is reviewed for both frequency and time domains. This part has three sections, namely, broadband dielectric spectroscopy, time-domain dielectric spectroscopy, and a section where different aspects of data treatment and fitting routines are discussed in detail. Then, some examples of dielectric responses observed in various disordered materials are presented. Finally, we will consider the experimental evidence of non-Debye dielectric responses in several complex disordered systems such as microemulsions, porous glasses, porous silicon, H-bonding liquids, aqueous solutions of polymers, and composite materials. 

The third relaxation process is located in the low-frequency region and the temperature interval 50°C to 100°C. The amplitude of this process essentially decreases when the frequency increases, and the maximum of the dielectric permittivity versus temperature has almost no temperature dependence (Fig 15). Finally, the low-frequency ac-conductivity ct demonstrates an S-shape dependency with increasing temperature (Fig. 16), which is typical of percolation [2,143,154]. Note in this regard that at the lowest-frequency limit of the covered frequency band the ac-conductivity can be associated with dc-conductivity cio usually measured at a fixed frequency by traditional conductometry. The dielectric relaxation process here is due to percolation of the apparent dipole moment excitation within the developed fractal structure of the connected pores [153,154,156]. This excitation is associated with the selfdiffusion of the charge carriers in the porous net. Note that as distinct from dynamic percolation in ionic microemulsions, the percolation in porous glasses appears via the transport of the excitation through the geometrical static fractal structure of the porous medium. 

Thus, the non-Debye dielectric behavior in silica glasses, PS and AOT microemulsions, has similar properties. These systems exhibit an intermediate temperature percolation process that is associated with the transfer of the electric... 

Differential scanning calorimetry (DSC) was used to determine the kinetics of polymerization and the glass transition temperature of the solid polymer. Preliminary results indicate the dependence of kinetics on the microstructure as determined using Borchardt and Daniels method (26). The reaction order, rate constant, and conversion were observed to be dependent on the initial microstructure of the microemulsions. The apparent glass transition temperature (Tg) of polystyrene obtained from anionic surfactant (SDS) microemulsions is significantly higher than the Tg of normal bulk polystyrene. In contrast, polymers from nonionic microemulsions show a decrease in Tg. Some representative values of Tg are shown in Table I. 

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