Nafion hypohalites

The perfluorinated ionomers containing sulfonate groups can be converted to the hypochlorite by reaction of the acid with ClF at low temperature. The hypochlorite can be converted to the hypobromite by reaction with a mixture of Br₂ and Cl₂. In this work Nafion - 511 manufactured by the DuPont Company was utilized. These unique hypohalites allow functionalization of the polymer in a variety of new reactions. Conversions of the Nafion hypobromite to the methyl and trifluoromethyl derivatives are described.     

An efficient copper-catalyzed coupling reaction of pyridin-2-ones with aryl and heterocyclic halides based on Buchwald's protocol

An efficient copper-catalyzed coupling reaction based on the Buchwald's protocol has been established for pyridin-2-ones with aryl iodides, aryl bromides, and heterocyclic bromides.     

Micro-interferometric backscatter detection using a diode laser

Micro-interferometric backscatter detection (MIBD) is performed with a simple, folded optical train based on the interaction of a diode laser beam and a fused silica capillary tube allowing for refractive index (RI) determinations and detection of optically active molecules in small volumes. Side illumination of the capillary by a laser produces a 360° fan of scattered light that contains two sets of high contrast interference fringes. These light and dark spots are viewed on a flat plane in the direct backscatter configuration. Signal interrogation for polarimetry is based on quantifying the relative intensities (depth of modulation (DOM)) of adjacent high frequency (HF) interference fringes for polarimetry and relative fringe position for RI detection. Positional changes of the interference pattern extrema (fringes) allow for the determination of Δn at the 10⁻⁷ level or 5.3 pmol or 0.48 ng of solute. The MIBD-RI detection volume is just 5.0 nl. DOM changes allow for optical activity detection limits of 5.7 × 10⁻⁵° (mandelic acid, []²³ = −153°, and D-glucose, []²⁵ = +52.5°), and a 2σ detection limit of 7.5 × 10⁻⁴ M (D-glucose) and 1.14 × 10⁻³ M (R-mandelic acid). The probe volume of MIBD-polarimetry was 38 nl, and within the probed volume at the limit of detection, about 28.7 pmol of mandelic acid or about 43.7 pmol of D-glucose is present. Furthermore, DOM (polarimetry signal) is unchanged when a non-optically active solute is interrogated by the MIBD-polarimeter. Finally, an optical model was derived and used to evaluate the advantages and pitfalls of using diode laser for MIBD.     

A versatile approach for the syntheses of poly(ester amide)s with pendant functional groups

Poly(ester amide)s (PEAs) are emerging as promising materials for a wide range of biomedical applications due to their potential for both hydrolytic and enzymatic degradation, as well as the ease with which their properties can be tuned by the choice of monomers. The incorporation of pendant functional handles along the PEA backbone has the potential to further expand their applications by allowing the charge and hydrophilicity of the polymers to be altered, and facilitating the conjugation of active molecules such as drugs, targeting groups, and cell signaling molecules. Described here is a simple and versatile strategy based on orthogonal protecting groups, by which L ‐lysine and L‐ aspartic acid can be incorporated into several families of PEAs based on monomers including the diacids succinic and terephthalic acid, the diols 1,4‐butanediol and 1,8‐octanediol, and the amino acids L‐ alanine and L‐ phenylalanine. All polymers were thoroughly characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. It was demonstrated that the side chain protecting groups could be readily removed, allowing the pendant amines or carboxylic acids to be functionalized. In particular, the carboxylic acid groups on a polymer containing L‐ aspartic acid units were converted to N‐hydroxysuccinimidyl esters, providing a useful template for further derivatization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3757–3772, 2009     

NMR and IR studies of bis((perfluoroalkyl)sulfonyl)imides

The influence of water on the NMR and IR spectra of bis((perfluoroalkyl)sulfonyl)imides has been investigated. The large effects of water on the observed spectra suggest that the proton is predominantly bound to the nitrogen of the perfluorosulfonimide acid in the absence of water, while it protonates water to form an onium salt in the presence of water.     

Aggregation of finite-size particles with variable mobility

New model equations are derived for dynamics of aggregation of finite-size particles. The differences from standard Debye-Hückel and Keller-Segel models are that the mobility of particles depends on the configuration of their neighbors and linear diffusion acts on locally averaged particle density. The evolution of collapsed states in these models reduces exactly to finite-dimensional dynamics of interacting particle clumps. Simulations show these collapsed (clumped) states emerge from smooth initial conditions, even in one spatial dimension. Extensions to two and three dimensions are also discussed.     

A study of association by hydrogen bonding in the system phenol-CCl4 by the nuclear magnetic relaxation method

The system phenol-CCl₄ was studied by measuring proton and deuteron magnetic relaxation rates and self-diffusion coefficients at 25°C. From these data intermolecular relaxation rates have been calculated. By means of an association parameter A, association of phenol molecules with respect to various parts of the molecule has been established. Closest distances of approach between protons and configurations of maximum occurrence probabilities are reported.