A conceptual model for forming surfaces with enantiomeric functionality from achiral molecules.

A means to form a surface with enantiomeric functionality using an achiral molecule is proposed. Specifically, if a meso compound were to be crystallized with the correct orientation, one set of opposing crystal faces would possess opposite handedness. This concept is a solid state analogue of a chromatographic device described previously.

Identification of a yellow impurity in aged samples of aqueous butamben suspension: evidence for the oxidative degradation of poly(ethylene glycol).

Butamben (butyl p-aminobenzoate) has been formulated to provide long-acting treatment for chronic pain. The suspension, which contains poly(ethylene glycol) and polysorbate 80, was found to yellow under ambient conditions if not adequately protected from oxygen. The impurity responsible for the color was isolated and identified on the basis of nuclear magnetic resonance spectroscopy and mass spectrometry. The compound is an oxalamidine, which is formally the condensation product of oxalic acid with four equivalents of butamben, and may be formed by the reaction of butamben with an oxidation product of poly(ethylene glycol).

Investigation of the in vitro release of gentamicin from a polyanhydride matrix.

Septacin¿trade mark omitted¿ is a sustained release formulation consisting of gentamicin sulfate dispersed in a biodegradable polyanhydride matrix. The polyanhydride matrix is a copolymer of erucic acid dimer (EAD) and sebacic acid in a 1:1 weight ratio. In vitro drug release was performed in both water and pH 7.4 phosphate buffer. The drug release in water was faster than that in the buffer, which was the opposite of what would be expected based upon a faster polymer hydrolysis rate in the buffer. Theoretical treatment of the data using the Peppas model revealed that release in water was anomalous, while the release in pH 7.4 phosphate buffer was diffusion-controlled. Profound bead morphology differences were observed between beads in these two in vitro release media. Cracking was observed in beads in water and swelling with no apparent cracking was seen in beads in buffer. Concurrent monitoring of drug and sebacic acid release indicated that drug release is not via surface erosion. Osmotic effects were found to play little role in the in vitro drug release. There was no spectroscopic evidence of amide formation between the drug and copolymer. Sulfate release was monitored along with drug release and the results indicate that there is ion-exchange occurring during the pH 7.4 in vitro release. It was subsequently demonstrated that gentamicin can form an insoluble salt with EAD. This salt formation explains the slower drug release in pH 7.4 phosphate buffer.

Thin Films of n-Si/Poly-(CH3)3Si-Cyclooctatetraene: Conducting-Polymer Solar Cells and Layered Structures.

The optical and electronic properties of thin films of the solution-processible polymer poly-(CH(3))(3)Si-cyclooctatetraene are presented. This conjugated polymer is based on a polyacetylene backbone with (CH(3))(3)Si side groups. Thin transparent films have been cast onto n-doped silicon (n-Si) substrates and doped with iodine to form surfacebarrier solar cells. The devices produce photovoltages that are at the theoretical limit and that are much greater than can be obtained from n-Si contacts with conventional metals. Two methods for forming layered polymeric materials, one involving the spincoating of preformed polymers and the other comprising the sequential polymerization of different monomers, are also described. An organic polymer analog of a metal/insulator/metal capacitor has been constructed with the latter method.