含有酯基及酰胺基柔链的苯并菲盘状液晶的合成、分子间氢键对柱状介晶性的影响

合成了三个系列, 共二十四个有两种不同软链的对称和非对称苯并菲盘状液晶化合物, C₁₈H₆(OR)₃- (OCH₂COOEt)₃, C₁₈H₆(OR)₃(OCH₂COOBu)₃, C₁₈H₆(OR)₃(OCH₂CONHBu)₃, 其中R＝C₅H₁₁, C₆H₁₃, C₇H₁₅, C₈H₁₇. 化合物通过柱层析纯化, 结构通过¹H NMR, IR, 元素分析等确证. 化合物热稳定性通过TGA测定, 并显示出较高的热稳定性. 通过偏光显微镜和差视扫描量热法对这些化合物的热致液晶性进行了研究. 结果显示: 对于苯并菲液晶化合物C₁₈H₆(OR)₃(OCH₂COOEt)₃, 非对称性化合物较之对称异构体化合物有更低的熔点和更高的清亮点, 因而非对称性化合物有更宽的介晶温度范围. 对于分子中含有酰胺基的苯并菲液晶化合物C₁₈H₆(OR)₃(OCH₂CONHBu)₃, 对称化合物有比非对称异构体更高的清亮点和更有序的六方柱状介晶相, 且其与具有同样软链长度的分子中不含酰胺基的化合物系列C₁₈H₆(OR)₃(OCH₂COOBu)₃相比较, 由于柱内分子间氢键的形成, 不仅有更高的熔点和清亮点, 而且有更丰富的柱状介晶相.     

六烷氧基取代的苯并菲和六氮杂苯并菲盘状液晶中的电荷转移

用电子转移的半经典模型在量子化学B3LYP/6-31G(d)水平(对单体)和B3LYP/STO-3G水平(对二聚物)对六烷氧基取代的苯并菲和六烷氧基取代的六氮杂苯并菲组成的盘状晶体系的电荷转移性质进行了研究,发现在用量子化学方法研究电荷转移反应时,不能简单地用氢氧基代替长链烷氧取代基。由于在电荷转移反应中,要考虑参与反应的分子之间前线轨道的细微差别,所以将长链取代基用氢氧基取代,可能得不到定性正确的结果。     

Charge Transport in Mesomorphic Phthalocyanines Studied by Pulse-Radiolysis Time-Resolved Microwave Conductivity

The pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique has been used to obtain information on the transport of charge within columnarly stacked, peripherally octaalkoxy-substituted phthalocyanines. Data are presented on the one-dimensional, intracolumnar charge mobility and on the timescale of quasi-two-dimensional intercolumnar electron tunnelling. Particular attention is paid to materials that are liquid-crystalline at room temperature, because of their potential technological importance in optoelectric charge transport layers and molecular semiconductor devices. The relevance of the data to channeled charge transport in aligned thin layers is discussed.     

5.4 Properties and applications of cellulose triacetate film

The CTA film can be characterized by e.g. its relatively high moisture regain, significantly low birefringence, and moderate mechanical strength. Having been commercialized more than fifty years ago, it has been widely used as photographic film, protective film for polarizing plate, and optical compensation film for liquid crystal display (LCD). The photographic film application exploits the optical isotropy and unique physical properties of the CTA film. In the application of the CTA film to protective film for polarizing plate, its low in-plane birefringence is of particular importance. In the optical compensation to enhance the viewing angle of LCD, the CTA film, because of its moderate retardation in thickness direction (Rth), serves as an element of compensator as well as a base film. Considering the growth of the LCD market, the demand for CTA film is believed to be further expanding.     

Do the molecules which form discotic liquid crystals have disc-like structures? The conformation of a simple model compound, 1,2-dihydroxydiacetylbenzene, determined from the NMR spectra of samples dissolved in liquid crystalline solvents

Many discotic mesogens are molecules with a central aromatic ring with adjacent alkylcarboxylate substituents. The simplest such molecule, 1,2-dihydroxydiacetylbenzene, which is not mesogenic, is studied by NMR spectroscopy as a solute in a nematic solvent. The spectra are analysed to give sets of residual dipolar couplings, D_ij , which are then used to test models for the conformation adopted by the acetate side groups. The conformations and geometry of an isolated molecule are calculated by the ab initio MP2/6-311G method and also by the DFT approach using the B3LYP functional with the 6-311++G** basis set. The quantum chemical calculations find that the minimum energy conformer has the acetate groups rotated in opposite directions out of the ring plane, and this kind of structure is also consistent with the NMR data.     

Synthesis and mesomorphism of ether–ester mixed tail C3-symmetrical truxene discotic liquid crystals

Truxene discotic liquid crystals are interesting for their polymesomorphism and as organic semiconductor candidates. We developed an efficient synthetic method for C₃-symmetrical truxene derivative 2,7,12-trihydroxy-3,8,13-trimethoxytruxene 5, and further a series of ether–ester mixed tail truxene discogens HTn, TR(OMe)₃[OOCC₆H₂(OC_nH_2n+1)₃]₃ were prepared. The truxene discogens HTn (n?=?4–8, 10, 12) were characterised by using ¹H and ¹³C nuclear magnetic resonance, and high-resolution mass spectrometry. Their thermal stability was studied with thermal gravimetric analysis and their liquid crystal properties were investigated by using polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. They exhibit a hexagonal columnar (Col_h) mesophase in fairly wide temperature ranges.     

Dye-sensitised solar cells with iodine-free discotic electrolytes

Discotic mesogenic molecules viz., hexahexylthiotriphenylene (HHTT) and hexahexyloxytriphenylene were applied, for the first time, as iodine-free redox electrolyte in dye-sensitised solar cells (DSSCs). The cell shows open circuit voltage (V_oc) of 0.95 V, short circuit current density (J_sc) of 0.534 mA/cm², fill factor 88.24% and overall power conversion efficiency (η) 0.45% in a typical fluorine doped tin oxide/TiO₂/N719/HHTT/Pt DSSC configuration. Scanning electron microscopy was used to study surface profile of electrolytes while electrochemical impedance spectroscopy was used to understand the electrochemical behaviour of electrolytes. The photovoltaic parameters were measured under standard conditions using Oriel solar simulator class AAA. These first results demonstrate the potential of the discotic molecules as charge transporter and mediator and show promise to be used in iodine-free DSSCs.     

Preparation and Photoluminescent Properties of Hydrogen-bonded Discotic Liquid Crystals

Photoluminescent discotic liquid crystals (DLCs) have been prepared through intermolecular hydrogen bonding between core and peripheral units. 1,3,5-Trihydroxybenzene was employed as core molecule and peripheral stilbazole derivatives containing linearly conjugated moieties were complexed to form hydrogen-bonded DLCs. Their structures, mesophases, and optical properties were investigated. The complexation of core and peripherals made some discotic complexes form photoluminescent DLCs. The prepared luminescent DLCs exhibited columnar mesophases with strong blue or sea green photoluminescence. These findings may contribute to the development of luminescent supramolecular liquid crystals for emitting materials in light emitting devices.     

Playing with nanosegregation in discotic crown ethers: from molecular design to OFETs,nanofibers and luminescent materials

Discotic liquid crystals are promising materials for electronic device applications. Combining extended π-systems with crown ethers may further open access to functional supramolecular hybrid materials. In the present publication, we briefly summarise recent literature developments and focus in a second part on our work in the field of discotic crown ethers. The crown ether derivatives are conveniently accessible by convergent syntheses which allow a high degree of variation with respect to side chains, mesogenic unit, size and symmetry of the crown core, metal complexation and counterion. This set of compounds provides a basis for systematic structure–property relationship investigations. Numerous experimental studies identified factors being crucial for mesophase stabilisation and geometry and furthermore led to novel room-temperature crown ether mesogens. The latter were obtained by congestion of the mesogenic units and even introduction of peripheral δ-methyl branched side chains. The formation of molybdenum clustomesogens and their application as luminescent hybrid materials is also described.