A series of highly soluble and fluorescent, at core tetraaryloxy-substituted and in imide positions hydrogen atom containing perylene bisimide (PBI) dyes 1a−e with varying peripheral side chains have been synthesized and thoroughly characterized. The self-assembly of these PBIs has been studied in detail by UV/vis, linear dichroism (LD) and circular dichroism (CD) spectroscopy, and scanning probe microscopy (AFM, STM). These studies revealed that the present PBIs self-assemble into extended double string cables, which consist of two hydrogen-bonded supramolecular polymeric chains of densely packed and strongly excitonically coupled PBI chromophores, providing highly fluorescent J-aggregates. The aggregation strength (“melting” temperature) and the fluorescence properties of these J-aggregates are dependent on the number and chain length of the peripheral alkoxy substituents, thus revealing a structure−property relationship. In contrast to previously reported assemblies of PBIs, for which the aggregation p...

Fluorescent J-Aggregates of Core-Substituted Perylene Bisimides: Studies on Structure−Property Relationship, Nucleation−Elongation Mechanism, and Sergeants-and-Soldiers Principle

New Hybrid Organic−Inorganic Solids with Helical Morphology via H-Bond Mediated Sol−Gel Hydrolysis of Silyl Derivatives of Chiral (R,R)- or (S,S)-Diureidocyclohexane

Chiral recognition in organogels occurs in the coassembly of the chiral gelator 1 with the chiral guest molecule 2. The diastereomeric aggregates formed from (R,R)-2 with (R,R)-1 or (S,S)-1 were found to be truly different in structure and strength. Cooperativity makes a major contribution to the chiral recognition in this system.

/pdf/chiral-recognition-in-bis-urea-based-aggregates-and-52q1xfbwbp.pdf

Chiral Recognition in Bis-Urea-Based Aggregates and Organogels through Cooperative Interactions.

Self-organized hybrid silica with long-range ordered lamellar structure.

Eleven bis-ureas have been synthesized, and some of their properties are reported. Several of these compounds form supramolecular polymers in organic solvents. The self-association is shown by FTIR spectroscopy to display cooperativity at two levels. The first level of cooperativity is due to the synergistic association of the two urea functions of a single molecule. The second level of cooperativity is revealed by the fact that the formation of dimers is less favored than that of long oligomers.

/pdf/highly-cooperative-formation-of-bis-urea-based-4svx8mfnsx.pdf

Highly cooperative formation of bis-urea based supramolecular polymers.

Structure of hydrogen-bonded sym-dialkylureas in nonpolar organic media

Volumes d'exces des melanges eau-butaneiols-1,2, -1,3 et -1,4, propanediol-1,3 et pentanediol-1,5

Excess molar volumes of binary mixtures of diols and water

A simple method for determination of the orientational order parameter in nematic liquid crystals is described. To determine the orientational order parameter S, we exploited the de Gennes observation, that any anisotropic physical quantity may be a measure of orientational ordering in the nematic phase. We prove that in the case of optical anisotropy, the discussion on microscopic level in determination of approximate S value can be omitted and the order parameter can be calculated directly from the macroscopic quantity measured in the experiment, i.e. the birefringence. A simple and precise method for the determination of the optical birefringence is described. Similarily as in the case of microscopic quantities, the value of anisotropic physical quantity for ideally ordered nematic can be extrapolated from its temperature dependence. Results obtained using the proposed method agree well with literature data. The method can be used also for the determination of orientational order parameter in cholesteric and some smectic liquid crystals.

Evaluation of the order parameter in nematic liquid crystals

Molecular structure of imide solutions: Part I. Propionimide in non-polar solvents

The magnetic Fredericksz transition in ferronematics (thermotropic nematic liquid crystals 7CB and MBBA combined with fine magnetic particles of size 10 nm) as a function of concentration of magnetic particles was studied by using simple dielectric measurements. The increase of the threshold magnetic field is observed in 7CB based ferronematic while the decrease of threshold field in MBBA based ferronematic is observed when the concentration of magnetic particles is increased. Experimental results are disscussed in framework of Brochard, de Gennes and Burylov, Raikher theories.

/pdf/study-of-magnetic-fredericksz-transition-in-ferronematics-4ex3pjzngv.pdf

B. Zywucki

Papers

Structure of hydrogen-bonded sym-dialkylureas in nonpolar organic media

Excess molar volumes of binary mixtures of diols and water

Evaluation of the order parameter in nematic liquid crystals

Molecular structure of imide solutions: Part I. Propionimide in non-polar solvents

Study of Magnetic Fredericksz Transition in Ferronematics. Liquid Crystals Doped with Fine Magnetic Particles