No abstract

No abstract

A series of achiral 4-biphenyl carboxylic acid compounds (BPCA-Cn-PmOH) connected with alkoxyl chains having various carbon numbers (n ) 6-10) and terminated by phenyl groups with meta-positioned hydroxyl groups was synthesized. Different phase structures including nematic, smectic A (SmA), smectic C (SmC), and highly ordered smectic liquid-crystalline phases along with crystalline phases were identified based on wide-angle X-ray diffraction and electron diffraction experiments. It was found via infrared spectroscopy that the hydrogen (H)-bonds were formed between the carboxylic acids to construct headto-head dimers as the building blocks for these ordered structural formations. H-bonds formed via the meta-positioned hydroxyl groups also played an important role in forming ordered layers in these structures. The morphology of this series of BPCA-Cn-PmOH as observed under polarized light microscopy showed an oily streak (cylinder) texture with Myelin-figure in the SmA phase. When temperature cools to enter the SmC phase, these streaks (cylinders) started to twist into helical suprastructures, which were not only by the birefringence changes but also by the three-dimensional helical geometry observed in other microscopic techniques. The dynamic conformational changes of the aromatic and aliphatic parts in this series of BPCA-Cn-PmOH at different temperatures correspond well with the thermal transitions via solid-state carbon-13 nuclear magnetic resonance experiments. Computer simulation indicated that the head-to-head dimers possess a twisted rather than a bent conformation. It was deduced that the twisted conformation of the dimers and the terminal meta-substituted phenyl groups at both ends of the dimers are critically important in forming the helical suprastructures.

A perylene-based reactive mesogen (DAPDI) forming a lyotropic chromonic liquid crystal (LCLC) phase was newly designed and synthesized for the fabrication of macroscopically oriented and patterned thin film polarizer (TFP) on the flexible polymer substrates. The anisotropic optical property and molecular self-assembly of DAPDI were investigated by the combination of microscopic, scattering and spectroscopic techniques. The main driving forces of molecular self-assembly were the face-to-face π-π intermolecular interaction among aromatic cores and the nanophase separation between hydrophilic ionic groups and hydrophobic aromatic cores. Degree of polarization for the macroscopically oriented and photopolymerized DAPDI TFP was estimated to be 99.81% at the λmax = 491 nm. After mechanically shearing the DAPDI LCLC aqueous solution on the flexible polymer substrates, we successfully fabricated the patterned DAPDI TFP by etching the unpolymerized regions selectively blocked by a photomask during the photopolymerization process. Chemical and mechanical stabilities were confirmed by the solvent and pencil hardness tests, and its surface morphology was further investigated by optical microscopy, atomic force microscopy, and three-dimensional surface nanoprofiler. The flexible and patterned DAPDI TFP with robust chemical and mechanical stabilities can be a stepping stone for the advanced flexible optoelectronic devices.

Supramolecular crystals were prepared via self-assembly of a series of inclusion complexes of β-cyclodextrin (β-CD) with poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO) block copolymer. In this study, two PEO-b-PPO-b-PEO copolymers were used with different molecular weights for the PEO blocks. On the basis of two-dimensional (2D) wide-angle X-ray diffraction (WAXD) and selected area electron diffraction (SAED) experiments, the supramolecular crystal structure was determined to be a monoclinic lattice with a = 1.910 nm, b = 2.426 nm, c = 1.568 nm, and β = 111°f or both inclusion complex systems. Each crystal unit cell contained four inclusion complexes. The space group was identified to be C 2 symmetry based on the relationship among diffraction spot intensity and systematic extinctions. With the help of computer simulations of the supramolecular structure, the packing of inclusion complexes in the crystal lattice could be achieved. The simulated 2D WAXD fiber patterns and SAED patterns agreed well with the experimental results. Observations of the morphology in transmission electron microscopy combined with the [001] zone SAED patterns indicated that the supramolecular crystals are lozenge-shaped, bound by four (110) planes. Furthermore, the tethered PEO blocks were found to crystallize, and the c-axis of the PEO crystals was nearly parallel to the lamellar surface normal of the supramolecular crystals. The existence of PEO crystals resulted in additional proof that β-CDs are only selectively threaded onto the PPO blocks when forming the inclusion complexes. These PEO crystals acted as locks to prevent the dethreading of the β-CDs from the complexes and physically stabilized the supramolecular structure.

Wearable technology offers new ways to be more proactive about our health and surroundings in real time. For next-generation wearable systems, robust storage and recording media are required to monitor and process the essential electrical signals generated under various unpredictable strain conditions. Here, we report the first fibriform organic transistor memory integrated on a thin and flexible metal wire. A capillary tube coating system allows the formation of a thin and nanograined organic ferroelectric film on the wire. The uniform morphology imparts excellent switching stability (∼100 cycles), quasi-permanent retention (over 5 × 10 4 s), and low-voltage operation (below 5 V) to the fibershaped memory devices. When sewn in a stretchable textile fabric, the memory fiber achieves long retention time of more than 10 4 s with negligible degradation of memory window even under a constant diagonal strain of 100% that exhibits reliable data storage under tough environments. These results illustrate the possibility of the practical, wearable fiber memory for recording electronic signals in smart garment applications.

A novel diamine, bis‐(3‐aminophenyl)‐4‐(trifluoromethyl)phenyl phosphine oxide (mDA3FPPO), containing phosphine oxide and fluorine moieties was prepared via the Grignard reaction from an intermediate, 4‐(trifluoromethyl)phenyl diphenyl phosphine oxide, that was synthesized from diphenylphosphinic chloride and 4‐(trifluoromethyl)bromobenzene, followed by nitration and reduction. The monomer was characterized by Fourier transform infrared (FTIR), 1H NMR, 31P NMR, 19F NMR spectroscopies; elemental analysis; melting point measurements; and titration and was used to prepare polyimides with a number of dianhydrides such as pyromellitic dianhydride (PMDA), 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethyliden]‐bis‐1,3‐isobenzofuranedione (6FDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′‐oxydiphthalic dianhydride (ODPA). Polyimides were synthesized via a conventional two‐step route; preparation of polyamic acids, followed by solution imidization, and the molecular weight were controlled to 20,000 g/mol. Resulting polyimides were characterized by FTIR, NMR, DSC, and intrinsic viscosity measurements. Refractive‐index, dielectric constant, and adhesive properties were also determined. The properties of polyimides were compared with those of polyimides prepared from 1,1‐bis‐(4‐aminophenyl)‐1‐phenyl‐2,2,2‐trifluoroethane (3FDAm) and bis‐(3‐aminophenyl) phenyl phosphine oxide (mDAPPO). The polyimides prepared from mDA3FPPO provided high glass‐transition temperatures (248–311 °C), good thermal stability, excellent solubility, low birefringence (0.0030–0.0036), low dielectric constants (2.9–3.1), and excellent adhesive properties with Cu foils (107 g/mm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3335–3347, 2001

For the construction of well-defined hierarchical superstructures of pristine [60]fullerene (C 60 ) arrays, pyrene-based molecular tweezers (PT) were used as host molecules for catching and arranging C 60 guest molecules. The formation of host−guest complexes was systematically studied in solution as well as in the solid state. Two-dimensional proton nuclear magnetic resonance spectroscopic studies revealed that PT−host and C 60 −guest complexes were closely related to the molecular selfassembly of PT. Ultraviolet and fluorescence spectroscopic titrations indicated the formation of stable 1:1 and 2:1 (PT/C 60 ) complexes. From the nonlinear curve-fitting analysis, equilibrium constants for the 1:1 (log K 1 ) and 2:1 (log K 2 ) complexes were estimated to be 4.96 and 5.01, respectively. X-ray diffraction results combined with transmission electron microscopy observations clearly exhibited the construction of well-defined layered superstructures of the PT−host and C 60 −guest complexes. From electron mobility measurements, it was demonstrated that the welldefined hierarchical hybrid nanostructure incorporating a C 60 array exhibited a high electron mobility of 1.7 × 10 −2 cm 2 V −1 s −1 . This study can provide a guideline for the hierarchical hybrid nanostructures of host−guest complex and its applications.