The high resolution infrared spectrum of 2-fluoroethanol (2FE) in a molecular beam was obtained in the region of 2990-2977 cm-1 . This spectral region contains the asymmetric CH stretch of the fluorinated carbon. Excitation of the CH stretch has previously been observed to photochemically isomerize 2FE from the Gg' to the Tt conformation. The high resolution spectrum of this transition provides the information necessary to quantitatively evaluate the amount of vibrational mode-coupling between the asymmetric CH stretch and the torsional reactive coordinate. Minimal amounts of vibrational mode-coupling was observed in the spectrum which is consistent with the slow photoisomerization rate. The correlation of the amount of mode-coupling and the isomerization rate supports the conclusion that mode-selective vibrational coupling plays an important role in the photochemical dynamics. It is further suggested that the strong intramolecular attractive interactions limit the magnitude of the vibrational mode-coupling.

The high resolution infrared spectrum of 1,2-difluoroethane (DFE) in a molecular beam has been obtained over the 2978-2996 cm-1 spectral region. This region corresponds to the symmetric combination of asymmetric C-H stretches in DFE. Observed rotational fine structure indicates that this C-H stretch is undergoing vibrational mode coupling to a single dark mode. The dark mode is split by approximately 19 cm -1 due to tunneling between the two identical gauche conformers. The mechanism of the coupling is largely anharmonic with a minor component of B/C plane Coriolis coupling. Effects of centrifugal distortion along the molecular A-axis are also observed. Analysis of the fine structure identifies the dark state as being composed of C-C torsion, CCF bend and CH2 rock. Coupling between the C-H stretches and the C-C torsion is of particular interest because DFE has been observed to undergo vibrationally induced isomerization from the gauche to trans conformer upon excitation of the C-H stretch.

High-performance surfactants have been developed for the preparation of water-in-oil high internal phase emulsions (HIPE), particularly for the preparation of polymerized HIPE foams. High-efficiency surfactants with poly(butylene oxide)/poly(ethylene oxide) (BO/EO) block copolymer backbones have been developed that can stabilize an HIPE through polymerization at concentrations as low as 0.006 wt% based on total emulsion weight. Polymerizable versions have been developed that bind into the polymeric foam backbone. BO/EO block copolymer surfactants also allow preparation of polymerized HIPE foams without salt in the aqueous phase. HIPE with the BO/EO surfactants have been prepared at room temperature and polymerized at temperatures exceeding 90°C. By minimizing the required amount of surfactant, allowing the surfactant to react during HIPE polymerizations, eliminating the need for salt, and stabilizing over a broad range of temperatures, BO/EO block copolymer surfactants have demonstrated their place as high-performance HIPE surfactants.Paper no. S1199 in JSD 4, 127-134 (April 2001) KEY WORDS: Polymerizable surfactants, polymerized water-inoil high internal-phase emulsions, poly(butylene oxide)/poly(ethylene oxide) surfactants.Emulsions comprise a continuous external phase and a discontinuous internal phase. High internal phase emulsions (HIPE) are a special type of emulsion wherein the internal phase makes up in excess of about 70 vol% of the emulsion. HIPE are routinely prepared with internal phases exceeding 98 vol%. The dispersed-phase droplets at these very high internal phase volumes are no longer free to move about in the external phase but are compressed against one another, taking on multifaceted geometries (1-3). The high-volume fraction of the dispersed phase in the HIPE led very early to their being considered for a variety of applications. Many of the applications utilized the shear thinning rheological properties of the HIPE (high viscosity at low shear rate and low viscosity at high-shear rates) (4). Some examples of this are: safety fuels (5), suspension media for transporting solids through pipelines (6-8), hydraulic fracturing of subterranean formations surrounding oil wells (9-11), cosmetic preparations (12), and emulsion explosives (13,14). In addition to the rheological properties, polymerized HIPE compositions found uses in other applications. Examples are: particles in the range of 0.1 to 0.3 µm (15), membranes for separation of water-ethanol mixtures by pervaporation (16), and polymeric foams for absorption of hydrophobic materials (17) and hydrophilic materials (18). The particles are obtained by polymerizing the dispersed monomers in an aqueous continuous phase, whereas the membrane and foams are obtained by polymerizing a continuous monomer phase in which an aqueous phase is dispersed. In all of these cases, the HIPE provides the template for the polymerization of the monomers. For the preparation of polymeric foams, the internal phase volume dictates the void volume of the foam, and the ...

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