Functional π-Gelators and Their Applications

Discotic Liquid Crystals.

This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

Ionic Liquid Crystals: Versatile Materials.

Since the discovery of the liquid-crystalline state of matter 125 years ago, this field has developed into a scientific area with many facets. This Review presents recent developments in the molecular design and self-assembly of liquid crystals. The focus is on new exciting soft-matter structures distinct from the usually observed nematic, smectic, and columnar phases. These new structures have enhanced complexity, including multicompartment and cellular structures, periodic and quasiperiodic arrays of spheres, and new emergent properties, such as ferroelctricity and spontaneous achiral symmetry-breaking. Comparisons are made with developments in related fields, such as self-assembled monolayers, multiblock copolymers, and nanoparticle arrays. Measures of structural complexity used herein are the size of the lattice, the number of distinct compartments, the dimensionality, and the logic depth of the resulting supramolecular structures.

Development of structural complexity by liquid-crystal self-assembly.

Large aggregates, constructed by linking together monomer building blocks via non-covalent interactions with polymer properties, are regarded as supramolecular polymers. Many kinds of non-covalent interactions, such as metal–ligand coordination, hydrogen bonding, π–π stacking, ionic interaction, and host–guest interaction etc., can be involved in the binding interactions of monomer building blocks, as well as in the modification of the side chain for the construction of variable supramolecular polymers. In this tutorial review, we summarized the reported supramolecular polymers fully- or partially-created from the combination of multiple non-covalent binding interactions, mainly of two kinds, in the orthogonal way.

Advanced supramolecular polymers constructed by orthogonal self-assembly

Suppression of Skin−Core Structure in Injection-Molded Polymer Parts by in Situ Incorporation of a Microfibrillar Network

This paper describes a system in which an acid functionalized discotic molecule and poly(propylene-imine) dendrimer self-assemble into a new type of oblique columnar liquid crystalline (LC) phase that displays a well-ordered superlattice. The orthogonal combination of hydrogen bonding in the columnar direction and ionic interaction in the plane perpendicular to the columns gives rise to a structure in which the dendrimer is confined to separate columnar domains. The structure of the mesophases formed in the mixed system has been elucidated by infrared spectroscopy and X-ray diffraction. Investigation by differential scanning calorimetry and polarizing optical microscopy has shown that the LC phase is most stable in an 8:1 molar mixture but remains stable over a wide temperature and composition range. In dendrimer enriched mixtures the lattice swells to take up more dendrimer, while discotic enriched mixtures show the appearance of lamellar phases with a columnar structure that is probably closely related ...

http://wimdejeu.nl/onewebmedia/all%20publications/144%20ChemMater%202008%20Fitie.pdf

Nanostructured Materials through Orthogonal Self-Assembly in a Columnar Liquid Crystal

The morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) (PCL-b-PEO) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy. The molecular masses Mn of the PCL and PEO blocks are 24 000 and 5800, respectively. X-ray scattering and rheological measurements indicate that no microphase separation occurs in the melt. Decreasing the temperature simultaneously triggers off a crystallization of PCL and microphase separation between the PCL and PEO blocks. Coupling and competition between microphase separation and crystallization results in a morphology of PEO spheres surrounded by PCL partially crystallized in lamella. Further decreasing temperature induces the crystallization of PEO spheres, which have a preferred orientation due to the confinements from hard PCL crystalline lamella and from soft amorphous PCL segments in different sides. The final morphology of this highly asymmetric block copolymer is similar to the granular morphology reported for syndiotactic polypropylene and other (co-) polymers. This implies a similar underlying mechanism of coupling and competition of various phase transitions, which is worth further exploration

/pdf/morphology-of-a-highly-asymmetric-double-crystallizable-poly-4p6jhi4sc0.pdf

Morphology of a highly asymmetric double crystallizable poly(ε-caprolactone-b-ethylene oxide) block copolymer

We provide evidence that earlier reported smectic ordering in the melt of isotactic polypropylene is not intrinsic to the system but results from the presence of small quantities of calcium stearate. No causal relation exists between this effect and the crystallization properties of iPP.

http://wimdejeu.nl/onewebmedia/all%20publications/140%20Macrom%202007%20Byelov.pdf

Shear-induced smectic order in isotactic polypropylene revisited

The thermotropic phase behavior of symmetric cyclohexanetriamides carrying various linear and branched alkyl chains was investigated using calorimetry, microscopy, solid-state NMR, dielectric relaxation spectroscopy, and X-ray scattering techniques. Cyclohexanetriamides carrying C6 or longer linear alkyl chains formed columnar plastic phases with a pseudocentered rectangular lattice. Those with C8 or longer alkyl chain also showed a nematic liquid crystalline phase. Cyclohexanetriamides carrying branched octyl chains displayed columnar phases with rectangular lattices, except for the triamide with the highly branched tetramethylbutyl group. The occurrence of less symmetrical columnar phases is ascribed to the mode of stacking of cyclohexanetriamides which leads to noncylindrical columns. Dielectric relaxation spectra also featured highly cooperative relaxation processes related to reorientation of the macrodipolar columns in the mesophase, showing the potential of these molecules as building blocks in res...

http://wimdejeu.nl/onewebmedia/all%20publications/151%20JPhysChemB%202009%20Tomatsu.pdf

Dmytro Byelov

Papers

Suppression of Skin−Core Structure in Injection-Molded Polymer Parts by in Situ Incorporation of a Microfibrillar Network

Nanostructured Materials through Orthogonal Self-Assembly in a Columnar Liquid Crystal

Morphology of a highly asymmetric double crystallizable poly(ε-caprolactone-b-ethylene oxide) block copolymer

Shear-induced smectic order in isotactic polypropylene revisited

Thermotropic phase behavior of trialkyl cyclohexanetriamides.