Synthesis of Mixed Tail Triphenylene Discotic Liquid Crystals： Molecular Symmetry and Oxygen-Atom Effect on the Stabilization of Columnar Mesophases

Small change in chemical structure of discotic liquid crystals can cause big difference in their mesomorphism. Replacing of the alkoxy peripheral chains of triphenylene by oxygen-atom containing ester chains would result in novel mesomorphism. A series of mixed tail triphenylenes containing propoxyacetyloxy and alkoxy, abbreviated as C18H6（OCnH2n＋1）3（OCOCH2OC3H7）3, n=4-8, and hexa（propyloxyacetyloxy）triphenylene, C18H6（OCOCH2OC3H7）6 were synthesized. Thermal gravimetry analysis （TGA） of three discogens showed that they had good thermal stability till 350 ℃. The mesomorphism was investigated through differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The preliminary X-ray diffraction （XRD） results of one compound showed that it exhibited ordered hexagonal columnar （Colho） mesophase. These mixed tail triphenylene derivatives possessed much stable Colho mesophase and wider mesophase ranges than their hexaalkoxytriphenylene C18H6（OR）6 and hexaalkanoyloxytriphenylene C18H6（OCOR＇）6 analogues. The asymmetrical compounds 2,6,11-trialkoxy-3,7,10-tri（2-propyloxyacetyloxy）triphenylenes with n=5-8 displayed higher clearing points and wider temperature ranges than their symmetrical isomers 2,6,10-trialkoxy-3,7,11-tri（2-propyloxyacetyloxy）- triphenylenes, while C18H6（OCOCH2OC3H7）6 had the highest clearing point due to the β-oxygen-atom effect.     

新的混合柔链苯并菲盘状液晶：分子对称性与宽温柱状介晶相

A series of new trialkoxytrialkanoyloxytriphenylene TP（OCnH2n＋1）3（OCOCmH2m＋1）3 （5a-5e） （n =m＋1 =4- 8） discotic liquid crystals were prepared and their mesomorphic properties were investigated using differential scanning calorimetry （DSC） and polarizing optical microscopy （POM）. The symmetrical and shorter chain triphenylenes display higher melting points and clearing points, more highly ordered and stable columnar mesophase than the asymmetrical and longer chain triphenylenes respectively.     

ORDERED STRUCTURAL EVOLUTION AND RELAXATION BEHAVIORS OF A SERIES MICROPHASE SEPARATED "HAIRY-ROD" POLYIMIDES WITH MULTIPLE ALKYL SIDE CHAINS

A series of "hairy-rod" polyimides, BBPA(n), with multiple alkyl side chains was prepared from 3,3′,4,4′biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-biphenyldiamine substituted in the 2,2′-positions with benzoate, which was substituted in the 3,4,5-positions with ether side chains of varying lengths. The number of the methylene units, n, in these alkyl side chains were in even numbers ranging from 8 to 18. Combining techniques of one-dimensional (1D) and 2D wide angle x-ray diffraction, 1D small angle X-ray scattering, differential scanning calorimetry experiments, it was found that this series of "hairy-rod" polyimides possess a micro-phase separation between the backbones and side chains. This led to the formation of ordered structures in two different lengthscales, of which both are hexagonal packing: one is attributed to the alkyl side chains on the sub-nanometer scale, and another is for the whole polymer chains on the nanometer scale. The development of the hexagonal structure on the sub-nanometer scale was critically dependent upon the lengths of the alkyl side chains. Three relaxation processes were captured by dynamic mechanical analysis, i.e., segmental motion of the backbones, α, the melting of the side chain crystals, β1, which exits only for the materials with longer side chains (n = 18,16); and the subglass relaxation of side chains,β2. The peak relaxation temperature of the α process decreased with increasing the length of side chains, while the one of theβ2 process increased. The activation energy of the αrelaxation was relatively independent on the length of side chain, whereas, β2 process showed the increasing of activation energy with increasing the length of side chains.     

Aggregating Properties of Compounds Cz—C—n in DMSO—H2O Binary Solvent

The aggregating properties of Cz-C-n(n=3,6,10) have been unvestigated by means of fluorescence method in DMSO-H2O binary solvent. The measured CAC and C Φ values indicate that the aggregating tendency of the amphiphilic compounds Cz-C-n containing crown ether increases with the length of alkyl chains, similar to that of carbazole compounds with long alkyl chains.     

ORDERED STRUCTURAL EVOLUTION AND RELAXATION BEHAVIORS OF A SERIES MICROPHASE SEPARATED “HAIRY-ROD” POLYIMIDES WITH MULTIPLE ALKYL SIDE CHAINS

A series of “hairy-rod” polyimides, BBPA(n), with multiple alkyl side chains was prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-biphenyldiamine substituted in the 2,2′-positions with benzoate, which was substituted in the 3,4,5-positions with ether side chains of varying lengths. The number of the methylene units, n, in these alkyl side chains were in even numbers ranging from 8 to 18. Combining techniques of one-dimensional (1D) and 2D wide angle x-ray diffraction, 1D small angle X-ray scattering, differential scanning calorimetry experiments, it was found that this series of “hairy-rod” polyimides possess a micro-phase separation between the backbones and side chains. This led to the formation of ordered structures in two different length scales, of which both are hexagonal packing: one is attributed to the alkyl side chains on the sub-nanometer scale, and another is for the whole polymer chains on the nanometer scale. The development of the hexagonal structure on the sub-nanometer scale was critically dependent upon the lengths of the alkylside chains. Three relaxation processes were captured by dynamic mechanical analysis, i.e., segmental motion of the backbones, α the melting of the side chain crystals, β1, which exits only for the materials with longer side chains(n=18,16); and the subglass relaxation of side chains, β2- The peak relaxation temperature of the α process decreased with increasing the length of side chains, while the one of the β2 process increased. The activation energy of the α relaxation was relatively independent on the length of side chain, whereas, β2 process showed the increasing of activation energy with increasing the length of side chains.     

Synthesis, two-photon absorption and AIE properties of multibranched thiophene-based triphenylamine derivatives with triazine core

Two new multibranched thiophene-based triarylamine derivatives with 1,3,5-triazine core are synthesized and characterized. Their one-and two-photon absorption properties and aggregation-induced emission effect have been investigated. Both the STAPA-based compounds are AIE active. The two-photon absorption (2PA) cross sections measured by the open aperture Z-scan technique are determined to be 620 and 1610 GM for STAPA-a and STAPA-b in chloroform,respectively, which dramatically increase with the introduction of alkyl chains. The relationship between their structures and properties on one-and two-photon absorption and aggregation-induced emission is discussed, which allows us to examine the effect of introducing alkyl chains. In addition, solvent effects also show a significant influence on the 2PA cross section. The two compounds with excellent AIE and 2PA properties provide attractive alternatives for the biophotonic materials.     

STUDY ON LIQUID CRYSTAL POLYMERS WITH TWO-DIMENSIONAL MESOGENIC UNITS

A series of liquid crystalline polymers with two-dimensional mesogenic units were synthesized by solution polycondensation at low temperature. All the polymers were liquid crystalline. The melting temperature T_m (except that with substituent of methoxy) and the clearing temperature T_i of the polymers change regularly with varying of the length of the alkyl substituent groups.     

Syntheses of Benzoxepinoquinolinone and Benzothiepinoquinolinone

l-Benzoxepino(3, 4-b)quinolin-l3(6H)-one and its halogen,alkyl, alkoxy derivatives Va'-d' and 1-benzothiepino(3,4-b}-quinolin- 13 ( 6H)-one Vf, and its alkyl derivatives Vg, weresynthesized through cyclization of 2-(substituted phenoxymethyl)-3-quinolinecarboxylic acids Va-d and 2-[ (un)substituted phen-ylthiomethyll-3-quinolinecarboxylic acids IVf-g in the presence ofpolyphosphoric acid.The acids IV were obtained from the corresponding ethyl-esters @ whcih were prepared through refluxing ethyl 2-bromo-methyl-3-quinolinecarboxylate(1) with substituted phenol or (un)substituted thiophenol in the presence of NaOEt.The compound Vg, was allowed to react with NBS, KaBH4, NH2OH-HCl to give compounds VII , VIII, and IX, respectively.The structures of 24 new compounds have been confirmed by elemental analysis, IR and 1H NMR.     

Synthesis of unsymmetric triphenylene discotic liquid crystals with a semi-fluorinated chain and the influence of fluorophobic effect on mesogenic behavior

The fluorophobic effect of the semi-fluorinated chain of discotic molecules efficiently improves the stability of columnar mesophase.Low symmetric discogens exhibit decreased melting points and wide mesophase ranges.A series of triphenylene derivatives 1,C18H6(OCnH2n+1)4(OMe)(O2CC2H4C6F13),and their hydrocarbon analogues 2,C18H6(OCnH2n+1)4(OMe)(O2CC8H17),n = 4―8,were synthesized for the investigation of the influence of semi-fluorinated peripheral chain and molecular symmetry on mesomorphism.The structures ...     

Synthesis of polyfluorenes bearing lateral pyreneterminated alkyl chains for dispersion of single-walled carbon nanotubes

Two kinds of polyfluorenes bearing two lateral pyrene terminated alkyl chains and two alkyl chains per repeating unit were synthesized by Suzuki polycondensation and used to disperse single-walled carbon nanotubes(SWCNT) in organic solvents.Stable polymer-SWCNT complex can be formed via the multivalentπ-πstacking interaction of the lateral pyrene functional groups and the polyfluorene backbone with the outer surface of carbon nanotubes;meanwhile the lateral alkyl chains can impart good solubility to the complex.As expected,polyfluorenes bearing lateral pyrene functional groups and octyl chains exhibited much higher carbon nanotube solubility in common organic solvents than the corresponding polyfluorenes bearing only octyl chains.Photophysical studies indicated that the formation of polymer-SWCNT complex can effectively quench the fluorescence of polyfluorenes.     

Alignment behaviour of symmetrical and asymmetrical triphenylenes possessing fluoroalkylated side chains on modified substrates

The alignment behaviour of triphenylene‐based compounds possessing fluoroalkylated and alkyl side chains was investigated for the hexagonal columnar (Col_h) mesophase on polyimide‐, cetyltrimethylammonium bromide (CTAB)‐, and indium tin oxide‐coated glass substrates by polarizing optical microscopy. It was found that 2,6,10‐trinonyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluorononyloxy)triphenylene and 2,6,11‐trinonyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluorononyloxy)triphenylene exhibit spontaneous homeotropic alignment on these substrates. On the other hand, it was found that 2,6,10‐triheptyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluoroheptyloxy)triphenylene, 2,6,11‐triheptyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluoroheptyloxy)triphenylene, 2,6,10‐trihexyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluorohexyloxy)triphenylene, 2,6,11‐trihexyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluorohexyloxy)triphenylene, 2,6,10‐tributyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluorobutyloxy)triphenylene and 2,6,11‐tributyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluorobutyloxy)triphenylene do not show such spontaneous homeotropic alignment on these substrates. These results indicate that the spontaneous homeotropic alignment of the Col_h phase could be easily attained by the introduction of an appropriate length of the fluoromethylene chains in the peripheral parts of discogens. Therefore, it is suggested that the balance between the hydrocarbon part including the triphenylene core and the fluoroalkyl part determines the alignment control behaviour. Furthermore, it was found that alignment behaviour is independent of the rotation symmetry of the chemical structure but is dependent on the number of fluoromethylene chains in the chemical structure.     

Alignment behaviour of symmetrical and asymmetrical triphenylenes possessing fluoroalkylated side chains on modified substrates

The alignment behaviour of triphenylene-based compounds possessing fluoroalkylated and alkyl side chains was investigated for the hexagonal columnar (Col_h) mesophase on polyimide-, cetyltrimethylammonium bromide (CTAB)-, and indium tin oxide-coated glass substrates by polarizing optical microscopy. It was found that 2,6,10-trinonyloxy-3,7,11-tris(1H,1H,2H,2H,3H,3H-perfluorononyloxy)triphenylene and 2,6,11-trinonyloxy-3,7,10-tris(1H,1H,2H,2H,3H,3H-perfluorononyloxy)triphenylene exhibit spontaneous homeotropic alignment on these substrates. On the other hand, it was found that 2,6,10-triheptyloxy-3,7,11-tris(1H,1H,2H,2H,3H,3H-perfluoroheptyloxy)triphenylene, 2,6,11-triheptyloxy-3,7,10-tris(1H,1H,2H,2H,3H,3H-perfluoroheptyloxy)triphenylene, 2,6,10-trihexyloxy-3,7,11-tris(1H,1H,2H,2H,3H,3H-perfluorohexyloxy)triphenylene, 2,6,11-trihexyloxy-3,7,10-tris(1H,1H,2H,2H,3H,3H-perfluorohexyloxy)triphenylene, 2,6,10-tributyloxy-3,7,11-tris(1H,1H,2H,2H,3H,3H-perfluorobutyloxy)triphenylene and 2,6,11-tributyloxy-3,7,10-tris(1H,1H,2H,2H,3H,3H-perfluorobutyloxy)triphenylene do not show such spontaneous homeotropic alignment on these substrates. These results indicate that the spontaneous homeotropic alignment of the Col_h phase could be easily attained by the introduction of an appropriate length of the fluoromethylene chains in the peripheral parts of discogens. Therefore, it is suggested that the balance between the hydrocarbon part including the triphenylene core and the fluoroalkyl part determines the alignment control behaviour. Furthermore, it was found that alignment behaviour is independent of the rotation symmetry of the chemical structure but is dependent on the number of fluoromethylene chains in the chemical structure.     

Synthesis and mesomorphism of mixed ether-ester tail triphenylene discotic liquid crystals with long alkyloxy peripheral chains

Symmetrical and asymmetrical triphenylene discotic liquid crystals with two kinds of different peripheral chains, sym-TP(OC₁₁H₂₃)₃(O₂CR)₃ and asym-TP(OC₁₁H₂₃)₃(O₂CR)₃, (R=CH₂OC₂H₅, CH₂OC₃H₇, CH₂OC₄H₉, CH₂OC₅H₁₁, C₃H₇, C₄H₉, C₅H₁₁, C₆H₁₃, C₇H₁₅) were synthesized. Their thermotropic liquid crystalline properties were studied by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The results showed that the asymmetrical compounds had higher melting and clearing points than that of their corresponding symmetrical compounds. For the same series of compounds, TP(OC₁₁H₂₃)₃(O₂CR)₃, their melting points decrease and clearing points increase gradually with the lengthening of ester chains. Most of the β-oxygen containing esters of triphenylene derivatives, TP (OC₁₁H₂₃)₃(O₂CR)₃, (R=CH₂OC₂H₅, CH₂OC₃H₇, CH₂OC₄H₉, CH₂OC₅H₁₁), symmetrically or asymmetrically attached on triphenylene cores, have higher melting and clearing points than those of triphenylene derivatives, TP(OC₁₁H₂₃)₃(O₂CR)₃, (R=C₄H₉, C₅H₁₁, C₆H₁₃, C₇H₁₅), with the same length of peripheral chains. The triphenylene derivatives with longer peripheral chains have shown mesophase at room temperature. __________ Translated from Chemical Research and Application, 2007, 19(10) (in Chinese)     

分子间氢键对苯并菲柱状介晶性的影响: 量子化学ONIOM (MO/MM)研究

我们最近的实验显示: 对于分子中含有酰胺基的苯并菲液晶化合物C₁₈H₆(OC₅H₁₁)₃(OCH₂CONHC₄H₉)₃, 对称化合物有比反对称异构体更高的清亮点和更有序的六方柱状介晶相, 且与具有同样软链长度的分子中不含酰胺基的化合物C₁₈H₆(OC₅H₁₁)₃(OCH₂COOC₄H₉)₃相比较, 有更高的清亮点和更丰富的柱状介晶相. 本文通过量子化学ONIOM (B3LYP/6-31G(d,p):UFF)计算, 说明对于带酰胺基的分子, 对称分子比反对称分子有较大的稳定化能和较高的转动势垒. 对于对称性分子, 带酰胺基的分子比带酯基的分子有较大的稳定化能和较高的转动势垒. 这说明由酰胺基形成的分子间氢键起了稳定液晶相和锚定六方柱状相的作用, 可以解释带酰胺基的分子和对称性分子有较高的清亮点和更有序的六方柱状介晶相. 如果加长酰胺基的软链, 则可使氢键锚定的扭转角减少, 这样有利于提高电荷传输速率.     

盘状液晶中间体单羟基苯并菲简便合成

羟基苯并菲[TP(OH)(OR)5]是一类重要的盘状液晶中间体. 根据苯并菲衍生物间极性差异, 设计了一条简便的合成与分离羟基苯并菲的方法: 在70%硫酸中用FeCl3氧化邻苯二醚与2-甲氧基苯酚三聚成环, 分离获得2,3,6,7,10,11-六烷氧基苯并菲[TP(OR)6]和2-羟基-3-甲氧基-6,7,10,11-四烷氧基苯并菲[TP(OH)(OMe)(OR)4]. 后者再经醚化, Ph2PLi脱甲基得2-羟基-3,6,7,10,11-五烷氧基苯并菲[TP(OH)(OR)5]. 三步反应总收率14%～19%.     

Synthesis and mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers

Connecting two discotic mesogens via a spacer not only stabilizes the columnar mesophase but also leads to the formation of glass columnar phase, and therefore improves the physical properties of discotic liquid crystals as organic semiconductor. Here, we report the synthesis of eight diacetylene-bridged triphenylene discotic liquid crystal dimers, [C18H6(OCnH2n+1)4(OMe)O2C-C8H16-C≡≡ C-]2, 3(n), (n = 4-8), [C18H6(OC6H13)5O2C-C8H16-C≡≡ C-]2, 6 and [C18H6(OC6H13)5O-(CH2)m-C≡≡ C-]2, 8(m), (m = 1, 3) by Eglinto...     

Controlled synthesis and microstructure tuning of PEG‐containing side‐chain discotic liquid crystalline block copolymers via RAFT polymerization

Liquid crystalline block copolymers (LCBCPs) are fascinating for their combining molecular level liquid crystalline orders and microphase separated multidomain morphologies. Here in this article, a series of PEG‐containing side‐chain discotic LCBCPs of PEG‐b‐P_m‐n with variant spacer length m = 6, 10 and degree of polymerization (DP) of discotic LC block from n = 10 to 45, have been well‐synthesized via reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. The RAFT process mediated by macromolecular chain transfer agent (macroCTA) shows remarkable monomer concentration dependence. The influence of the introduced PEG block on the nano‐scale microphase‐segregation and mesophase organization is closely related to the side‐chain triphenylene (TP) discogens stacking mode dependent on the spacer length. Wherein, the PEG‐b‐P₆‐n series with a six‐methylene spacer exhibit consistent microphase separation with slightly disturbed yet ordered columnar structures. While for PEG‐b‐P₁₀‐n series with a longer ten‐methylene spacer, the columnar organization in the copolymers is even improved in contrast with the low order of randomly TP stacking in their corresponding homopolymers. This work offers a viable and inspiring pathway for controlled synthesis of block copolymers with bulky side groups, as well as enhances in‐depth understanding of the hierarchical superstructure organization in discotic units involved complex block copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2544–2553     

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.