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 cryst...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(OC n H2n+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 Eglinton coupling reaction. The thermotropic liquid crystal properties were studied by differential scanning calorimetry and polarized optical microscopy. The results are showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers; dimers 3(n) (n = 5–8) and 6 had glass columnar phase, and no crystallization was observed above ?50°C for all the triphenylene dimers; compared with 3(6), 6 showed higher molecular symmetry, more stable columnar mesophase and wider mesophase range. The connecting group, length and rigidity of spacer had important influence on the mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers.展开更多
As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an ...As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an optical study of two nematogenic compounds of this series viz., 6.O12O.6 and 7.O12O.7 by carrying out the measurement of extraordinary and ordinary refractive indices using modified spectrometer. The molecular polarizability anisotropies are evaluated using Lippincott δ-function model, the molecular vibration method, Haller’s extrapolation method and scaling factor method. The molecular polrizabilities, αe and αo are calculated using Vuks’ isotropic field model and Neugebauer’s anisotropic field model. The orientational order parameter, S, is estimated by using the molecular polarizability values calculated from refractive index and denstity data as well as polarizability anisotropy values calculated as a function of temperature in the nematic phase of both of the dimers. These values are discussed with reference to the order parameter values obtained directly from the optical birefringence, Δn, data without assuming any internal field. A comparison of the order parameter values from all of these methods was carried out in the light of available literature data.展开更多
A novel phosphorescent cyclometalated platinum dimer with bis-[2-（p-dodecyloxyphenyl） pyridyll-hexane-1,6-diol as ligand and 1,3-（1-n-hexyl,3-n-heptadecyl）diketone as ancillary ligand was synthesized.The chemical ...A novel phosphorescent cyclometalated platinum dimer with bis-[2-（p-dodecyloxyphenyl） pyridyll-hexane-1,6-diol as ligand and 1,3-（1-n-hexyl,3-n-heptadecyl）diketone as ancillary ligand was synthesized.The chemical structure and liquid crystal property of the dimer were characterized by ~1H NMR,ESl-MS,polarizing optical microscopy（POM） and differential scanning calorimetry （DSC）.The aligned film of title compound on the rubbed polyimide film is intensely emissive at room temperature with emission maximum at 516nm.The luminescence dichroic ratio（（？） ） at 516 nm is 3.1.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.50473062,50673069,and 50811140156)
文摘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(OC n H2n+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 Eglinton coupling reaction. The thermotropic liquid crystal properties were studied by differential scanning calorimetry and polarized optical microscopy. The results are showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers; dimers 3(n) (n = 5–8) and 6 had glass columnar phase, and no crystallization was observed above ?50°C for all the triphenylene dimers; compared with 3(6), 6 showed higher molecular symmetry, more stable columnar mesophase and wider mesophase range. The connecting group, length and rigidity of spacer had important influence on the mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers.
文摘As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an optical study of two nematogenic compounds of this series viz., 6.O12O.6 and 7.O12O.7 by carrying out the measurement of extraordinary and ordinary refractive indices using modified spectrometer. The molecular polarizability anisotropies are evaluated using Lippincott δ-function model, the molecular vibration method, Haller’s extrapolation method and scaling factor method. The molecular polrizabilities, αe and αo are calculated using Vuks’ isotropic field model and Neugebauer’s anisotropic field model. The orientational order parameter, S, is estimated by using the molecular polarizability values calculated from refractive index and denstity data as well as polarizability anisotropy values calculated as a function of temperature in the nematic phase of both of the dimers. These values are discussed with reference to the order parameter values obtained directly from the optical birefringence, Δn, data without assuming any internal field. A comparison of the order parameter values from all of these methods was carried out in the light of available literature data.
基金supported by the National Natural Science Foundation of China(Nos.20472060 and 21072141)Basic Research Fund of Education Bureau of Sichuan Province,China(No.08ZA040).
文摘A novel phosphorescent cyclometalated platinum dimer with bis-[2-（p-dodecyloxyphenyl） pyridyll-hexane-1,6-diol as ligand and 1,3-（1-n-hexyl,3-n-heptadecyl）diketone as ancillary ligand was synthesized.The chemical structure and liquid crystal property of the dimer were characterized by ~1H NMR,ESl-MS,polarizing optical microscopy（POM） and differential scanning calorimetry （DSC）.The aligned film of title compound on the rubbed polyimide film is intensely emissive at room temperature with emission maximum at 516nm.The luminescence dichroic ratio（（？） ） at 516 nm is 3.1.
