Heuristics for precise supramolecular control of soft matter structure and properties - 2,3,4-tris(dodecyloxy)benzenesulfonates with alkaline and organic cations.

Comprehensive analysis of the structure and phase behavior for a number of 2,3,4-tris(dodecyloxy)benzenesulfonates with alkali metal and organic focal groups revealed that the shape of the mesogenic group plays a decisive role in phase behavior of the material. Cubic and layered types of packing prevail when the size of the cation is small and, thus, the shape of the mesogenic molecule is close to conic one. With increasing cation size, the shape becomes more tapered, and columnar mesophases appear to be more stable. Interactions of the focal groups however determine the stability of mesophases. Comparatively strong interactions may, morever, provide substantial deviations from a phase diagram plotting the transition temperatures versus the radius of focal group, as in the case of pyridinium 2,3,4-tris(dodecyloxy)benzenesulfonate.

Disodium 4,5,6-trihy-droxy-benzene-1,3-disulfonate dihydrate.

In the title compound, 2Na(+)·C(6)H(4)O(9)S(2) (2-)·2H(2)O, the benzene rings of the 4,5,6-trihy-droxy-benzene-1,3-disulfonate ions, which are stacked parallel to each other forming rods parallel to the a axis, are slightly deformed (planarity, symmetry) mainly because of the high degree of substitution. The two sodium ions, located within pockets of the anion rods, are coordinated by six and seven O atoms, resulting in octa-hedral and penta-gonal-bipyramidal coordinations, respectively. In addition to these coordinative bonds towards sodium, an extended network of intra- and inter-molecular hydrogen bonds occurs.

Synthesis, aggregation, and adsorption phenomena of shape-persistent macrocycles with extraannular polyalkyl substituents.

The synthesis of shape-persistent macrocycles based on the phenyl-ethynyl backbone containing various extraannular alkyl side chains is described. Although compound solubility increases with increasing size of the side groups, decreasing the solvent polarity induces aggregation of the rings by nonspecific interactions. This was investigated by proton NMR spectroscopy. The magnitude of aggregation can be varied by using solvent mixtures of different hexane content, supporting the model of a solvophobic effect. From 1,2,4-trichlorobenzene solution the macrocycle 1c adsorbs at the surface of highly oriented pyrolitic graphite (HOPG). The two-dimensional order of the structure was investigated by scanning tunneling microscopy (STM) revealing the formation of a two-dimensional lattice of p1(2)mm symmetry with lattice parameters A = 3.6 nm, B = 5.7 nm, and Gamma = 74 degrees.

Bis[(alkoxy)benzoylsemicarbazides]--a new class of powerful organogelators.

Reaction of N-[(alkoxy)benzoyl]hydrazides and diisocyanates produces bis[(alkoxy)benzoylsemicarbazides] that allow for 'cold gelation' of organic liquids by mixing low viscous gelator solutions with a large excess of the respective solvent at ambient temperature.

Synthesis and characterization of tris-methacrylated 3,4,5-tris

The synthesis of liquid crystalline 3,4,5-tris(11-methacryloylundecyl-1-oxybenzyloxy)benzoic acid, 2-methyl-(1,4,7,10,13-pentaoxacyclopentadecane)-3,4,5-tris[4-(11-methacryloylundecyl-1-oxy)benzyloxy] benzoate and its 1:1 complex with sodium triflate is described. The observed mesophases were identified, by polarized optical microscopy and contact preparation techniques, to be of hexagonal columnar disordered structure. The amphiphiles form lyotropic columnar phases in concentrated methacrylate solvents, while at low solute contents supramolecular organogels emerge.

Field-cycling NMR relaxometry of molecules undergoing Lévy walks at the surface of fine particles and porous glass.

Slow surface dynamics of solvents confined in the pore space of porous glass and fineparticles was studied by proton field-cycling relaxometry. Molecular reorientations mediated by translational displacements are shown to be an important low-frequency T1-relaxation mechanism in porous media at low nuclear magnetic resonance (NMR) frequencies in the strong adsorption limit. This is revealed by the pronounced T1-dispersion in this case while a flat one is observed for weak adsorption. The following nanoporous materials were examined in this respect: fineparticles of ZnO,-TiO2, porous glass. Silanized surfaces lead to a somewhat steeper T1-dispersion of non-polar cyclohexane than the native, i.e. polar, surfaces. On the other hand, there is no strong influence of the surface groups on the T1(omega) slope of (polar) acetone. The results are discussed with reorientations mediated by translational displacements enhanced by Lévy walks on the surface.

Comparing the effects of perinatal and later childhood lead exposure on neuropsychological outcome.

Blood lead values (PbB) from cord blood and maternal samples as well as present PbB from venous blood samples were available for 114 six- to seven-year-old children living in or near the city of Nordenham (FRG). These children represented 30% of all children born between July 1975 and August 1976 in the district hospital (N = 383). The range of cord blood PbB was 4-31 micrograms/100 ml (mean = 8.2 micrograms/100 ml) and of maternal PbB was 4-30 micrograms/100 ml (mean = 9.3 micrograms/100 ml), whereas the range for present PbB was 3.9-22.8 micrograms/100 ml (mean = 8.2 micrograms/100 ml). The degree of correlation between maternal and cord blood PbB was 0.79, despite the poor technical quality of many cord blood samples as compared to maternal blood samples (less coagulation). These children were given a battery of neurophysiological and neuropsychological tests. The present report is restricted to psychological performance measures. The test battery covered intelligence (reduced Wechsler Intelligence Scale for Children), visual-motor performance (Bender Test, GFT), serial reaction performance (Wiener Reaction Device), and cued as well as choice reaction times. After correction for confounding by means of stepwise multiple-regression analysis, few significant associations between blood lead levels and performance deficit occurred. In general the degree of association was somewhat stronger for present PbB than for perinatal PbB: With increasing present PbB there was a borderline drop of performance IQ (P less than 0.1), as well as a significant disruption of serial reactions, which was more pronounced for the difficult (P less than 0.01) than for the easier version of the Wiener Device (P less than 0.05). A similar but less pronounced pattern of associations was observed for maternal PbB but not for cord blood PbB. Some influence of perinatal lead exposure on later performance can, thus, still be detected if, in addition to cord blood PbB, maternal PbB is taken into account as well.