12 research outputs found
Scanning pyroelectric microscopy revealing the spation polarity distribution in topologically centric crystals of trans-4-chloro-4 -nitrostilbene
Reversible sorption of nitrogen and xenon gas by the guest-free zeolite tris(o-phenylenedioxy)cyclotriphosphazene (TPP)
Influence of the solvent of crystallization on the orientational disorder of (trans)-4-chloro-4’-nitrostilbene
Orientational Disorder of (trans)-4-Chloro-4’-nitrostilbene: A Detailed Analysis by Single Crystal X-ray Diffraction
Structural relaxation in nanometer thin layers of glycerol
The molecular dynamics in nanometer thin films of glycerol was investigated upon thickness reduction by combining organic molecular deposition with in situ broadband dielectric spectroscopy. Changes in the cooperative dynamics with respect to bulk glycerol were observed for films of thicknesses down to 1.6 nm (corresponding to roughly three molecular layers). Systematic investigation revealed no pure size effects addressable merely to geometrical constraints. However, an increase in the glass transition temperature by 3.5 K was observed for the thinnest film, indicating the presence of a layer with reduced mobility in close proximity to the substrate. The impact of both the upper and lower interfaces has been disentangled by measurements performed during slow desorption. Moreover, proof is given for the existence of a layer with enhanced mobility in the vicinity of the free surface enslaved to the dynamics of the rest of the film. © 2010 American Chemical Society.status: publishe
Preparation of donor–acceptor substituted fluorostilbenes and crystal chemistry of fluorinated (E)-4-(4-halogeno-styryl)-benzonitriles
The syntheses and crystal structures of a series of fluoro-substituted halogeno (Cl, Br, I)-cyano-stilbenes containing donor and acceptor groups (D-π-A) are reported. These molecules show a tendency to form antiparallel chain-like structures and herringbone packing, crystallising predominantly in a centric space group. However, second harmonic generation measurements bear evidence for orientational disorder leading to partial polar order below the ordinary X-ray structure determination limit. Some co-crystals are isostructural with their components. The non-fluoro as well as the halogeno-fluoro substituted components of co-crystals seem to impose their crystal structure on the complementary fluoro- or cyano–fluoro substituted components. Co-crystallization enhanced the deviation from centrosymmetry