Jianxun Wen

Synthesis of (p-substituted-tetrafluorophenyl)ethynes and diacetylene monomers containing fluoro-aromatic rings by nucleophilic substitution on [(pentafluorophenyl)ethynyl]-trimethylsilane

Abstract Substitutions on [(pentafluorophenyl)ethynyl]trimethylsilane (1) with nucleophiles, Nu-X (2) give the corresponding [(p-substituted-tetrafluorophenyl)ethynyl]trimethylsilanes (3) or (p-substituted-tetrafluorophenyl)ethynes (4) . The trimethylsilyl group of (3) can be easily removed by treatment with dilute alkali to give [(p-substituted-tetrafluorophenyl)ethynes (4) . Diacetylenes containing fluoro-aromatic rings are prepared by the Chodkiewiez-Cadiot and the Hay coupling of the corresponding terminal acetylenes (4) .

Novel fluorinated liquid crystals. Part I. Synthesis of compounds possessing (p-substituted-tetrafluorophenyl)ethyne substituents as materials for liquid crystals

Abstract [4-(2,3,5,6-Tetrafluoro-4′-octyloxybiphenylyl)] [4-alkoxycarbonylphenyl]acetylenes have been prepared via a Pd-catalyzed coupling, reaction. These compounds form mesomorphic phases over a wide temperature range and provide a new series of liquid crystal materials containing 1,4-tetrafluorophenylene in their basic structure.

Synthesis and transition temperatures of novel fluorinated chiral liquid crystals containing 1,4-tetrafluorophenylene units

Abstract To continue the search for novel series of fluorinated ferroelectric liquid crystals, an additional two series of 4-[(S)-2-methylbutoxy]phenyl 4-[(4-n-alkoxy-2,3,5,6-tetrafluorophenyl)ethynyl] benzoates (C) and 4-(n-alkoxy)phenyl 4-[(4-(S)-2′-methylbutoxy-2,3,5,6-tetrafluorophenyl)] benzoates (D) have been synthesized. Polarizing microscopic textural observations and DSC measurements of the phase transitions of these novel compounds showed that compounds C were liquid crystals with a chiral nematic (N) phase and a monotropic chiral smectic C phase (Sc), and compounds D exhibited a chiral nematic (N) phase.

Novel fluorinated liquid crystals. Part VI. The synthesis and phase transition of novel cholesteric liquid crystals containing 1,4-tetrafluorophenylene units

Abstract 1-[(4-n-Alkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]-4-[(4-(( S )-2-methylbutoxy)-2,3,5 ,6-tetrafluorophenyl)ethynyl]benzenes have been prepared from the starting material 1-pentafluorophenyl-2-trimethylsilylacetylene. Textural observation by polarizing microscopy showed that these materials were cholesteric liquid crystals when the terminal alkoxy chains were of sufficient length. The effect of symmetrical tetrafluoro substitution of phenyl groups on the mesomorphic behaviour is also discussed.

Synthesis of substituted polyfluoro-aromatic acetylenes

Abstract Reaction of pentafluoro-aromatic acetylene compounds with large excesses of nucleophilic agents using K 2 CO 3 as base gave polysubstituted and monosubstituted polyfluoro-aromatic acetylenes.

Synthesis of 1,4-bis(p-aryloxy-tetrafluorophenyl)butadiyne monomers for nonlinear optics

Abstract Novel diacetylenes with polyfluorophenyl groups directly bound to the diacetylene moiety, 1,4-bis(p-aryloxy-tetrafluorophenyl)butadiynes, were prepared in four steps from pentafluoroiodobenzene and trimethylsilylacetylene.

Synthesis of asymmetric polyfluoro-diacetylene monomers

Abstract Asymmetric diacetylene monomers with polyfluoro-aromatic rings for nonlinear optics were prepared by the cross coupling of 1-bromo-acetylenes with polyfluoro-aromatic acetylenes which were prepared by nucleophilic substitution on pentafluorophenyltrimethylsilylacetylene.

Solvatochromic behavior of a novel soluble polydiacetylene with 2,4,6-tri(4-n-heptylphenyloxy)-3,5-difluorophenyl units directly attached to the conjugated backbone

Abstract The solvatochromic transition of a new polydiacetylene, with 2,4,6-tri(4-n-heptylphenyloxy)-3,5-difluorophenyl groups directly attached to the conjugated backbone, is described.

Third-order nonlinear optical properties of new soluble poly 1,4-bis[2,4,6-tri(4-n-heptylphenyloxy)-3,5-difluorophenyl]butadiyne

Abstract A new soluble polydiacetylene with fluoro-aromatic rings directly attached to the π-conjugated main-chain backbone was synthesized by γ-radiation solid-state polymerization. The blue thin films of poly(fluorophenyl-diacetylene) could be only obtained from its red chloroform solution by a spin-coating technique. The third-order nonlinear optical susceptibilities of spin-coated amorphous thin films of poly (fluorophenyl-diacetylene) were measured by third-order harmonic generation. The third-order nonlinear optical coefficient susceptibility χ (3) calculated by comparing the 3ω signal intensity of sample with that of a standard fused silica plate, was about 6.4 × 10 −11 esu.

Nonlinear optical properties of poly(fluorophenyl- diacetylene) evaporated films

Abstract A new insoluble polydiacetylene with fluoro-aromatic units directly bound to the π-conjugated main backbone has been obtained via solid-state polymerization induced by UV light, daylight and γ-rays. Third-order harmonic generation has been measured on poly(fluorophenyl-diacetylene) films prepared by the vacuum deposition method. The third-order nonlinear optical susceptibility of this poly(fluorophenyl-diacetylene) film was evaluated as χ (3) = 7.3 × 10 −11 esu.