The synthesis and characterization of two families of ionic liquid crystal dendrimers consisting of the ammonium salts of the commercially available poly(amidoamine) (G = 0-5) and poly(propylene imine) (G = 1-5) dendrimers and three long-chain carboxylic acids are reported. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing light optical microscopy, and X-ray diffractometry. The thermal stability of the ionic materials was further studied by NMR. Most of the dendrimers show lamellar mesomorphism, and two of them exhibit columnar mesomorphism. On the basis of the experimental results, we propose models both at the molecular level and in the mesophase for all the materials.

In this tutorial review we describe some studies concerning liquid crystal dendritic polymers. We have chosen to present several representative examples that illustrate the diverse kinds of LC dendritic structures, namely: dendrimers, dendrons, dendronized polymers and hyperbranched polymers. We review their synthesis, mesogenic properties and the way that they are arranged to form supramolecular liquid crystal assemblies.

A key parameter in the performance of organic electronics devices is the mobility of charges. On the macroscopic level, it has been demonstrated that the highest charge carrier mobilities are obtained in highly ordered single-crystalline materials.[1] However, the inherent fragility of single crystals poses serious technological problems, thus considerably limiting their practical applications. An interesting alternative is offered by discotic mesogens, which are typically composed of a central aromatic core substituted with flexible alkylic chains.[2] Cores tend to form columnar stacks, maximizing porbital overlap between adjacent molecules and thus favoring a one-dimensional migration of charge carriers.[3] Furthermore, the inherent fluidity of liquid crystals induces advantageous properties, such as the ability to self-heal structural defects and easier alignment and processing from the isotropic phase. However, fluidity is also associated with intrastack dynamism of the functional units that reduces carrier mobility in the bulk. Therefore, the preferred strategy for improving mobility in discotic mesophases has been the enhancement of the intermolecular order within the stacks. To achieve this goal, different approaches have been explored: 1) linking the cores to peripheral alkylic chains through bulky moieties; [4] 2) introducing functional groups providing directional interactions [5] (e.g. hydrogen bonds); or even 3) inducing helical columnar arrangements that provide a higher degree of order. [4a, 6, 7] Herein, we present an experimental study on new triindole mesogens, one of them exhibiting very high hole mobility (m % 1.4 cm 2 V À1 s À1 ). We show how carrier mobility in such compounds does not depend only on the degree of intracolumnar order along the columns by itself, but also, as in most p-conjugated organic semiconductors, on the stacking distance between molecules, which usually decreases with increasing order.[8] Moreover, results show how intracolumnar molecular distance can be controlled by a suitable choice of the spacers between the aromatic core and the peripheral chains, underlining the promising role of ethynyl moieties as linkers in high-mobility columnar phases.Heptacyclic 10,15-dihydro-5H-diindolo[3,2-a:3',2'-c]carbazole (triindole) was recently introduced as a new core for discotic mesogens.[9] Attachment of six decyl chains (compound 1 in Scheme 1) resulted in columnar hexagonal mesophases, although no stacking periodicity was observed. Despite the intracolumnar disorder, 1 has a high hole mobility m = 0.02 cm 2 V À1 s À1 in the mesophase. In an attempt to raise the mobility values by increasing intracolumnar order, we have investigated the effect of sterically demanding phenyl (compound 2) and rigid alkyne (compound 3) spacers between the peripheral alkyl chains and the central triindole core.The synthesis of 2 and 3 is described in the Supporting Information. Both compounds are obtained as crystalline solids. On heating, they show mesomorphic behavior between room temperature and ...

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The synthesis and characterization of a new family of ionic liquid crystal dendrimers consisting of the ammonium salts of the commercially available poly(propylene imine) (G ) 1-5) dendrimers and 4-decyloxy-, 3,4-didecyloxy-, and 3,4,5-tridecyloxybenzoic acids are reported. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing-light optical microscopy, and X-ray diffractometry. Dendrimers with mono-and didecyloxybenzoate moieties show lamellar mesomorphism, namely, smectic A, whereas those with tridecyloxybenzoate units show columnar mesomorphism: rectangular for G ) 1 and hexagonal for G ) 2-5. On the basis of the experimental results, we propose models both at the molecular level and in the mesophase for all the materials.

Communications ADVANCED MATERIALSsured reflections in the range 2 I 0 I 26'. 962 symmetry-independent reflections with I > 3 0 (I) used, without absorption correction ( p = 4.6 cm-I), in the structure solution (direct methods: SHELX-86) and least-squares refinement (SHELX-76) of 109 parameters. S and C atoms relined anisotropicdlly; H atoms, located in AFmaps, refined isotropically through some least squares cycles, and then held fixed. R = 0.029

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As part of our research on new ferroelectric liquid crystalline materials, we present the synthesis, characterization, and physical properties of a new family of polymeric materials, namely AB block copolymers consisting of a non-liquid crystalline chain [poly(isobutyl vinyl ether)] and a chiral liquid crystalline block. The combination of both features gives rise to the appearance of interesting effects on the properties of the polymers:  they show the ferroelectric chiral smectic C mesophase at room temperature with low viscosities and low birefringence, due to the presence of the non-liquid crystalline chain. The chiral smectic C phase exhibits the characteristic switching under electric fields. Its electro-optical behavior has been characterized and is different than that of the parent homopolymer. The block copolymers show the typical microphase separation of the two blocks which has been observed by small angle X-ray scattering.