Twisted smectic A phases in side chain liquid crystal polymers

The syntheses of two side chain liquid crystal polymers, a polyacrylate and a polymethacrylate, are reported. In each of the polymers the liquid-crystalline side group carries an asymmetric carbon atom, thereby making some of the liquid crystal phases formed by the polymers optically active and chiral. For the chiral polyacrylate smectic A and chiral ferroelectric smectic C phases are observed, however for the chiral polymethacrylate a cholesteric phase is detected above the smectic A phase. It is found that the smectic A to cholesteric phase transition is mediated by the formation of an intermediary twisted smectic A phase. This intermediary phase is a liquid-crystalline analogue of the Abrikosov flux phase found in Type II superconductors.     

Measurement of N-methyl-2-pyridone-5-carboxamide in urine by high performance liquid chromatography

We have previously described a simple and reproducible method for the measurement of nicotinamide and its major metabolite N-methyl-2-pyridone-5-carboxamide (2-pyr) in human plasma. We now describe a low-cost high-throughput method for measurement of urinary 2-pyr, and demonstrate that Isolute C18 bulk can replace use of the column to clean up the samples prior to injection into the HPLC apparatus. Using a standard curve together with an internal standard for each sample, with mean recovery of 2-pyr greater than 95%, the assay has proved reproducible, with considerable savings in cost and time. The principal advantages of this method are the rapid column clean up of samples prior to injection and the simple but effective methodology.     

X-ray and multinuclear NMR study of the mixed aggregate [(Ph2P(O)N(CH2Ph)CH3) · LiOC6H2-2,6-{C(CH3)3}2-4-CH3) · C7H8]2: a model for the directed metalation of phosphinamides

The addition of LiBuⁿ to a toluene solution of Ph₂P(O)N(CH₂Ph)CH₃1 and 2,6-di-tert-butyl-4-methylphenol 5 leads to the formation of the mixed dimer [(Ph₂P(O)N(CH₂Ph)CH₃) · LiOC₆H₂-2,6-{C(CH₃)₃}₂-4-CH₃) · C₇H₈]₂6. The single crystal X-ray structure shows that two lithium aryloxide moieties dimerize giving rise to a Li₂O₂ core in which each lithium atom is additionally coordinated to a phosphinamide 1 ligand. The multinuclear magnetic resonance study (¹H, ⁷Li, ¹³C, ³¹P) indicates that the solid-state structure is preserved in toluene solution. Complex 6 may be considered as a model for the pre-complexation step preceding the metalation of phosphinamides by an organolithium base.     

Homolytic reactions of polyfluoroaromatic compounds Part VIII. The decomposition of benzoyl peroxide in hexafluorobenzene

The decomposition of benzoyl peroxide in hexafluorobenzene proceeds by a spontaneous first-order process accompanied by an induced decomposition showing 1.5-order dependence upon the concentration of the peroxide. The induced decomposition is associated with the formation of 2,2′,3,4,5,6-hexafluorobiphenyl and benzoic acid. 2,3,4,5,6-Pentafluorobiphenyl is the main product at all concentrations of peroxide; small amounts of other compounds are formed, together with a high-boiling residue probably containing isomeric dodecafluorotetrahydroquaterphenyls. The mechanism is discussed.