Organic semiconducting materials offer the advantage of solution processability into flexible films. In most cases, their drawback is based on their low charge carrier mobility, which is directly related to the packing of the molecules both on local (amorphous versus crystalline) and on macroscopic (grain boundaries) length scales. Liquid crystalline ordering offers the possibility of circumventing this problem. An advanced concept comprises: i) the application of materials with different liquid crystalline phases, ii) the orientation of a low viscosity high temperature phase, and, iii) the transfer of the macroscopic orientation during cooling to a highly ordered (at best, crystalline-like) phase at room temperature. At the same time, the desired orientation for the application (OLED or field-effect transistor) can be obtained. This review presents the use of molecules with discotic, calamitic and sanidic phases and discusses the sensitivity of the phases with regard to defects depending on the dimensionality of the ordered structure (columns: 1D, smectic layers and sanidic phases: 2D). It presents ways to systematically improve charge carrier mobility by proper variation of the electronic and steric (packing) structure of the constituting molecules and to reach charge carrier mobilities that are close to and comparable to amorphous silicon, with values of 0.1 to 0.7 cm(2)  · V(-1)  · s(-1) . In this context, the significance of cross-linking to stabilize the orientation and liquid crystalline behavior of inorganic/organic hybrids is also discussed.

A silica monomer-estrone complex (EstSi) having a thermally cleavable urethane bond and a cross-linkable triethoxysilane group was synthesized. From EstSi and TEOS, spherical silica particles with sizes of 1.5-3 mum were prepared. The template molecules were removed from the silica matrix by heating at 180 degrees C in DMSO in the presence of water, generating a cavity with an amino group. The control silica particles that had the same sizes and shapes were obtained with aminopropyl triethoxysilane and TEOS. When ethylene glycol was added in place of H2O, an ethyl alcoholic group was formed in the cavity. Their recognition ability and specific binding for estrone were characterized by uptake experiments. The estrone-imprinted silica particles showed a much higher recognition ability than the control silica particles and higher selectivity for estrone than testosterone propionate.

Microporous polymers based on 1,3,5‐triazine units are prepared by Friedel‐Crafts reaction of 2,4,6‐trichloro‐1,3,5‐triazine with aromatic compounds. 2,4,6‐Trichloro‐1,3,5‐triazine is polymerized with benzene, biphenyl, and terphenyl in dichloromethane in the presence of aluminum chloride. The surface areas of the polymers are in the range of 558 to 1266 m2 g−1, depending on the aromatic linker length. At ambient pressure and temperature, the polymers exhibit high CO2 uptakes of 38–51 cm3 g−1. The CO2 uptake is significantly enhanced by 70–90% for the polymers carbonized at 400 °C for 1 h and at 800 °C for an additional 1 h under nitrogen. This result suggests that rigid microporous polymers can be used as precursor polymers for the synthesis of advanced porous carbon materials without the activation process.

No abstract

Triangular ortho-phenylene ethynylene (o-PE) cyclic trimers represent a novel member of shape-persistent macrocycles. Shape-persistent cyclic structures remain of great interest as molecular components in the fields of supramolecular materials, host-guest chemistry, and materials science. Novel discotic liquid crystalline properties are reported from triangular-shaped o-PE macrocycles containing branched alkoxy- and/or triethylene glycol (TEG) side chains using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The macrocycles self-assemble into thermotropic rectangular columnar (Colr) (for M1), hexagonal columnar (Colh) (for M2), and discotic nematic (for M3) mesophases at room temperature. This work shows clearly that electron-rich PE macrocycles can form LC materials. Alkyl side chains in M1 promote order, while hydrophilic side chains of M2 generate an amphiphilic structure that provides a different driving force for organization. The ability to create ordered self-assembling materials from these novel electron-rich macrocycles is important in nanotechnology.

No abstract

No abstract

Aromatic alternating copolyimides have been synthesized by the reaction of various precursors for imido diamine with GFDA. The alternating copolyimides appeared to have enhanced solubility in organic solvents such as NJV-dimethylacetamide (DMAc), N-methylpyrrolidinone (NMP), and dimethyl sulfoxide (DMSO) when compared with the corresponding random isomers. Various NMR experiments including 2-D COSY spectra have been performed for the characterization of the alternating copolyimides. On the basis of the NMR results, the synthetic pathway of the aromatic copolyimide through the reaction of a precursor for imido diamine with a dianhydride leads to a copolymer with a complete alternating sequence without randomization during the cyclization reaction. The glass transition temperatures of the alternating copolyimides obtained by DSC measurements showed values similar to those of the corresponding random ones. The decomposition behavior obtained by TGA exhibited close degradation temperatures of the alternating copolyimides regardless of the monomers used.