A one-phase microemulsion composed of a hybrid fluorocarbon/hydrocarbon surfactant CyFisCHCOSOs--Na+)C7His, water, and COa solubilizes substantial amounts of water. For example, the water-to-surfactant ratio in a single phase microemulsion is as high as 32 at 25 °C and 231 bar, compared with a value near 0 for more than 150 previously studied surfactants for temperatures up to 50 °C. Also with 1.9 wt % surfactant, up to 2 wt % water is soluble, which is 10 times the amount soluble in pure CO2. The requirements for the design of surfactants that form microemulsions in CO2 are examined.

Nanostructures of polyaniline (PAni) and polypyrrole (PPy) with controlled morphologies have been synthesized on atomically flat surfaces using adsorbed surfactant molecules as templates. Atomic force microscopy (AFM) has been used to investigate polymer film formation on highly oriented pyrolytic graphite (HOPG) and chemically modified HOPG. Morphological control over the resulting polymer film is possible by the addition of coadsorbing molecules, manipulation of the length of the surfactant hydrophobe, or by changing the surface chemistry of the adsorbing substrate. Phase transitions between spheres, cylinders/wires, and featureless films have been observed which exactly parallel transitions between spheres, cylinders, and flat layers in the adsorbed surfactant. Parallel arrays of PAni nanowires can be synthesized with alignment evident over large areas in a simple self-assembly technique in which fabrication and arrangement take place simultaneously. Such a technique in which one can engineer sub-100-nm-ordered nanoscale pi-conjugated polymer structures of a desired shape by a simple self-assembly process presents potential as templates, sensors, and microelectronic devices.

Surfactant bilayers are proposed as two-dimensional solvents for the formation of ultrathin films from surfactant, monomer, and substrate systems. Results from polymerization of styrene in sodium dodecyl sulfate bilayers adsorbed on alumina show 75% and higher conversions of adsolubilized monomer to polymer after 25 min. Uniform films of 3.4-3.6-nm thickness were formed on aluminum oxide layers on glass slides for reaction times of 30-45 min. Under varying conditions film thicknesses of 13.0 nm were also obtainable.

The objective of this study was to evaluate the attachment, proliferation, and differentiation of rat mesenchymal stem cells (MSC) toward the osteoblastic phenotype seeded on polypyrrole (PPy) thin films made by admicellar polymerization. Three different concentrations of pyrrole (Py) monomer (20, 35, and 50 x 10(-3) M) were used with the PPy films deposited on tissue culture polystyrene dishes (TCP). Regular TCP dishes and PPy polymerized on TCP by chemical polymerization without surfactant using 5 x 10(-3) M Py, were used as controls. Rat MSC were seeded on these surfaces and cultured for up to 20 d in osteogenic media. Surface topography was characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and static contact angle. Cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium content were measured to evaluate the ability of MSC to adhere and differentiate on PPy-coated TCP. Increased monomer concentrations resulted in PPy films of increased thickness and surface roughness. PPy films generated by different monomer concentrations induced drastically different cellular events. A wide spectrum of cell attachment characteristics (from excellent cell attachment to the complete inability to adhere) were obtained by varying the monomer concentration from 20 m to 50 x 10(-3) M. In particular the 20 x 10(-3) M PPy thin films demonstrated superior induction of MSC osteogenicity, which was comparable to standard TCP dishes, unlike PPy films of similar thickness prepared by chemical polymerization without surfactant. Adhesion of mesenchymal stem cells on tissue culture plates (TCP) coated with polypyrrole thin films made by admicellar polymerization.

Two homologous series of double-tail hybrid surfactants containing a hydrocarbon chain and a fluorocarbon chain attached to the same hydrophilic head group have been synthesized. The micellar solutions of such hybrid surfactants have been studied by conductance, surface tension, 19F NMR and 'H NMR. The dependence of the cmc on the chain length follows Klcven's equation. The micellar aggregation numbers are 10-35 and become smaller as the chain length increases. When the hydrocarbon chain bears three carbons or more, both the fluorocarbon and the hydrocarbon chains are incorporated inside the micelle. IntroductionThere has been a continuous effort in industry to prepare new formulations of detergents by changing the compositions of the surfactants, builders, and additives. However, there is relatively little development in the synthesis and characterization of new surfactants that have unusual structures, properties, and applications. The hybrid surfactants described in this paper represent part of our effort in this direction. They are composed of a hydrocarbon (HC) chain and a fluorocarbon (FC) chain attached to the same hydrophilic head group and are a new category of compounds which have not been explored previously.Doubletail surfactants with two HC chains attached to a sulfate head group have been studied by Winsorl and Evans2 in the 1950s. These homologous compounds of sodium dialkyl sulfate have the structural formulae RR'CHOS03Na, in which R and R' are unbranched HC chains with R having a longer chain length than R'. The hybrid surfactants reported here have similar structures, except that one of the chains is an unbranched FC chain.It has long been noticed that fluorinated surfactants are particularly efficient in lowering surface tension. Normally, in the mixture of a FC surfactant with a suitable HC surfactant, the FC surfactant reduces the surface tension while the HC surfactant aids in the reduction of the interfacial tension. The net result can be a system that easily wets and spreads on otherwise hard-tewet ~urfaces.~ However, for ionic surfactants with the same headgroup charge, the application of this advantage of combined effect is limited because of the demixing of HC/FC mixed surfactants. To overcome this problem, some single-chain surfactants containing a FC segment and a HC segment were synthesized, and they show good wettability on solid substrates containing FC ~omponents.~ Recently, Abenin and Cambon reported the synthesis of a series of double-tail HC/FC surfactants R&&NHCH2CHOHCH2NRI "Rm5 Such surfactants are very effective in lowering the surface tension or interfacial ten~ion.~ To our knowledge, hybrid surfactants containing separate FC and HC chains attached to the same head group have not been reported. In the present work, the synthesis, characterization, and the micellar properties of a homologous series of novel double-tail hybrid surfactant are described: