In this study, we report the use of ionic liquids as modifiers in the separation of achiral and chiral analytes in micellar electrokinetic chromatography. In this investigation, polymeric surfactants and ionic liquids were added to a low-conducting buffer solution. The polymeric surfactants used in this study were poly(sodium N-undecylelinic sulfate) and poly(sodium oleyl-l-leucylvalinate). The ionic liquids used in this study were chosen because of their high conductivity, hydrophobicity, and good solvating properties. Thus, it was expected that these ionic liquids would have the ability to assist in the separation of hydrophobic mixtures while maintaining adequate background current. Three analyte mixtures were separated using various buffer combinations of polymeric surfactant and ionic liquids. The ionic liquids were shown to improve the resolution and peak efficiency of the analytes while maintaining adequate background current.

Transmission gratings were formed holographically in polymer dispersed liquid crystal (HPDLC) composite materials using commercially available UV-curable acrylate monomers and the nematic liquid crystal TL203. Monomer mixtures with average functionality ranging from 1.3 to 3.5 were used to prepare HPDLC transmission gratings. The phase-separated morphology and surface topology of the transmission gratings as observed through scanning electron microscopy and atomic force microscopy varied profoundly with the different monomer mixtures characterized by their average functionalities. The switching properties of the HPDLC gratings were correlated with the morphological changes.

The present study explores the utility of the Test of Everyday Attention for Children (TEA-Ch) as a measure of the attentional impairments displayed by children with Attention Deficit Hyperactivity Disorder (ADHD). Sixty-three children with ADHD and 23 non-ADHD Clinical Control children were compared on subtests of the TEA-Ch reflecting three attentional domains: sustained, selective, and attentional control. Results show that children with ADHD performed significantly worse than clinical controls on subtests of sustained attention and attentional control. The groups did not differ, however, on subtests of selective attention. These findings suggest that the TEA-Ch is sensitive to attentional deficits unique to ADHD and holds promise as a useful tool in the assessment of ADHD. Performance patterns and future directions are discussed.

We report on the morphological and thermal properties of polymer-dispersed liquid crystals (PDLCs) fabricated with frontal-polymerization-induced phase separation (FPIPS). Frontal polymerization is characterized by a rapid-conversion, high-temperature, and large-thermal-gradient environment. A comparison is made between the morphological and thermal properties of PDLCs fabricated with FPIPS and traditional thermal-polymerization-induced phase separation. Characterization includes differential scanning calorimetry to probe the glass and nematic-to-isotropic transitions and scanning electron microscopy to evaluate the phase-separated morphology. In addition, the frontal temperatures and velocities are reported for PDLCs fabricated with frontal polymerization.

An achiral monomeric surfactant (sodium 10-undecenyl sulfate, SUS) and a chiral surfactant (sodium 10-undecenoyl L-leucinate, SUL) were synthesized and polymerized individually to form poly-SUS and poly-SUL. These surfactants were then copolymerized at various molar ratios to produce a variety of copolymerized surfactants (CoPSs), possessing both achiral (sulfate) and chiral (leucinate) head groups. The CoPSs, poly-SUS, poly-SUL, and sodium dodecyl sulfate were characterized using several analytical techniques. The aggregation numbers of the polymeric surfactants and the partial specific volumes were determined by the use of fluorescence quenching and density measurements, respectively. These polymeric surfactants were investigated as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC) for the separation of chiral and achiral solutes. Solute hydrophobicity was found to have major influence on the MEKC retention of alkyl phenyl ketones. In contrast, hydrogen-bonding ability of benzodiazepines is the major factor that governs their retention, but hydrophobicity has an insignificant effect on MEKC retention of benzodiazepines.

Sodium di(undecenyl) tartarate monomer (SDUT), a vesicle-forming amphiphilic compound possessing two hydrophilic carboxylate head groups and two hydrophobic undecenyl chains gemini surfactant, was prepared and polymerized to form a polymeric gemini surfactant (i.e., poly-SDUT). These anionic surfactant systems with carboxylate (SDUT and poly-SDUT) and sulfate (sodium dodecyl sulfate, SDS) head groups as well as mixed surfactant systems (SDS/SDUT, SDS/poly-SDUT, and SDUT/poly-SDUT) were then applied as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC). The SDUT and poly-SDUT were characterized using various analytical techniques. Retention factors of 36 benzene derivatives were calculated in 20 mM phosphate buffer of each surfactant system. The retention factor values of the test solutes show that there are distinctive selectivity differences between the surfactant systems. Solute-pseudostationary phase interactions in MEKC were also examined by determining the free energy of transfer of the substituted functional groups from the aqueous buffer phase into the pseudostationary phase.

No abstract

One disadvantage of amino acid-based chiral selectors for micellar electrokinetic chromatography (MEKC) is that either they have very low solubility or are insoluble at acidic pHs. In order to increase solubilities at lower pHs, we have synthesized a highly water-soluble achiral surfactant and copolymerized it with an amino acid-based chiral surfactant. These two surfactants were polymerized either separately or at various molar rations of binary solutions, yielding pure molecular or copolymerized surfactant (CoPS), respectively. All surfactants were characterized by use of several analytical techniques prior to using them as novel pseudostationary phases in MEKC. The chromatographic performance of the CoPS in MEKC was tested with chiral and achiral analytes. The highly soluble sulfate head group significantly increased the solubility of amino acid-based CoPS over a wide range of pH. Three chiral binaphthyl derivatives were tested and each surfactant system was found to have different selectivity.