169556-13-2Relevant academic research and scientific papers
Thermotropic side-chain liquid crystalline copolymers containing both mono- And bisazobenzene mesogens: Synthesis and properties
Cojocariu, Cristina,Rochon, Paul
, p. 9526 - 9538 (2008/02/01)
The synthesis of a novel series of copolymers containing push-pull bisazobenzene (BAz) and monoazobenzene (MAz) groups with various N-alkyl donor groups and with spacers of two and four methylene units is presented, and the effects of the structural variables on the mesomorphic properties of the polymers are investigated. The copolymer with very short spacer (n = 2) and bulky N-ethyl group exhibits liquid crystalline (LC) properties when the BAz content is at least 30 mol %. Replacing the N-ethyl group with N-methyl increases the tendency toward smectic mesomorphism and expands the mesophases stability. If the flexible spacer is extended to four methylene units, the glass transition temperature (Tg) decreases strongly, whereas the isotropization temperature (Ti) is only slightly affected. X-ray diffraction investigations reveal an orthogonal partial bilayer smectic phase in which the mesogens are interdigitated. Annealing the BAz polymer films above Tg brings about the out-of-plane (homeotropic) orientation of chromophores and the formation of H-aggregates.
Synthesis and characterization of a series of azobenzene-containing side-chain liquid crystalline polymers
Freiberg, Stephan,Lagugne-Labarthet, Francois,Rochon, Paul,Natansohn, Almeria
, p. 2680 - 2688 (2007/10/03)
A series of poly{4′-{(X-methacryloyloxyalkylene)methylamino}-4-nitroazobenzene} (pXMAN, where X is the number of methylene units and varies from 2 to 12) polymers with liquid crystalline (LC) properties was synthesized. When annealed above their Tg values, the whole series of polymers exhibits a stable smectic A mesophase while only the material with the shorter spacer, p2MAN, presents a smectic phase followed by a nematic phase. The spacing of the smectic layers was determined by X-ray diffraction, revealing intermolecular reorganization by interdigitation of the side-chain mesogens since the smectic layer spacing was larger than a fully extended side chain but less than two extended chains. This behavior is confirmed by temperature dependent aggregation as observed by UV-visible spectroscopy during the transition from an amorphous state to a liquid crystalline phase. The stability of the mesophase is enhanced by intermolecular interactions as argued by enthalpic and thermochromic considerations. Systematic photoinduced birefringence measurements on the various states reveal that the maximum and remnant levels of birefringence decrease with increasing the spacer length and with decreasing the glass transition temperature of the considered liquid crystalline polymer.
Photocleavage of the C-O bond of 9-phenanthrylmethyl ω-anilinoalkyl ethers via photo-induced intramolecular electron transfer
Sugimoto, Akira,Kimoto, Satoshi,Adachi, Tomohiro,Inoue, Hiroo
, p. 1459 - 1466 (2007/10/02)
Photoreactions of the title compounds nNHPh: Ar = 9-phenanthryl> 1 and 2 (n = 4 and 5) gave ω-alkan-1-ols 7 and 8 and ω-alkan-1-ols 9 and 10, respectively, by the cleavage of the C-O bond, while that of another title compound 3 (n = 6) gave spiro-compounds 17 and 18 with 12- and 14-membered-rings, respectively, as main products.The photoreaction is proposed to proceed via photo-induced intramolecular electron transfer from comparison of the reaction products with those in the photoreaction of ArCH2O3Ph 5 in the presence of N-methylaniline and acetic acid.The structures of spiro-compounds 17, 18, and the acetate of 9 were confirmed by X-ray crystal structure analysis.
