Chiral nematic organo-siloxane oligopodes based on an axially chiral binaphthalene core

The synthesis of a novel class of organosiloxane oligopodes, based on an axially chiral binaphthalene core is described and their mesogenic properties are fully characterised.     

Deviating behaviour of bromocarbethoxycarbene in cycloaddition reactions

The effect of Me substituents at alkenes 4 on the rates and activation parameters of cycloaddition reactions of bromocarbethoxycarbene (3) is very small. This carbene does not fit into the general equation (b) and the isoselective relationship (c) of dihalocarbenes. The deviating behaviour can be explained by a diffusion controlled reaction rate of bromocarbethoxycarbene.     

Modulation of the absorption, fluorescence, and liquid-crystal properties of functionalised diarylethene derivatives

Systematic variation of the molecular symmetry in a photochromic system based on a 1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluorocyclopentene group, connected by decyl spacers to two cyanobiphenyl groups as mesogens, allows for a systematic investigation of the correlations between molecular shape and symmetry, electronic effects, photochromic conversion and liquid-crystalline properties.     

Full miscibility of disk- and rod-shaped mesogens in the nematic phase

Mesogens containing rod-shaped moieties as well as one disk-shaped group exhibit nematic phase behavior and are entirely miscible with rod- and disk-shaped mesogens in the nematic phase. In the phase diagram, an extra nematic phase appears at nearly equimolar disk-rod ratios, where the nematic biaxial phase has been predicted.     

Solubility and glass transition in the system α-D-trehalose/water

Precipitation of trehalose dihydrate in water is observed at room temperature for trehalose concentrations higher than 47.5%w/w. Direct observations of crystal melting in water and measures of the solution density determine the thermal variations of trehalose saturationS(T) (mM) in water: ln(S(T))=ln(0.1223)-(1330/T) withR ² =0.9982. The glass transition (T_g) curve measured by DSC is lower at low concentrations and higher at high concentrations than previously reported.T _g is also measured as a function of the cooling/warming rates. Analysis of specific heat changes atT _g and associated activation energy leads to identify a most stable glassy state around the second eutectic concentration.     

Invariant Maximal Positive Subspaces and Polar Decompositions

It is proved that invertible operators on a Krein space which have an invariant maximal uniformly positive subspace and map its orthogonal complement into a nonnegative subspace allow polar decompositions with additional spectral properties. As a corollary, several classes of Krein space operators are shown to allow polar decompositions. An example in a finite dimensional Krein space shows that there exist dissipative operators that do not allow polar decompositions.     

Completely miscible disc and rod shaped molecules in the nematic phase

Disc and rod shaped molecules which are completely miscible in the nematic phase were synthesised and the miscibility behaviour was investigated and confirmed by POM, DSC and XRD studies.