• Title, Summary, Keyword: nitroazobenzene

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A Study on the Langmuir-Blodgett Films of Polyamic Acid Monolayer Containing p-Nitroazobenzene (p-Nitroazobenzene을 함유한 Polyamic Acid 단분자층의 Langmuir-Blodgett 막에 관한 연구)

  • Park, Keun-Ho
    • Journal of the Korean Applied Science and Technology
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    • v.28 no.2
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    • pp.213-218
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    • 2011
  • Displacement current measuring technique has been applied on the study of polyamic acid monolayer containing p-nitroazobenzene. The displacement current was generated from monolayer on the water surface by monolayer compression and expansion. Maxwell displacement current(MDC) was generated when the area per molecule was about $200{\AA}^2$ and $70{\AA}^2$. Maxwell displacement currents were investigated in connection with monolayer compression cycles. It was found that the maximum of MDC appeared at the molecular area just before the initial rise of surface pressure in compression cycles. The monolayer surface morphology of the LB film have been measured by Atomic Force Microscope(AFM). As a result, we confirmed that the microscopic properties of LB film by AFM showed the good orientation of monolayer molecules and the thickness of monolayer was 3.5-4.1nm.

Kinetics of the Rearrangement of $\beta$-4-Nitroazoxybenzene in Strongly Acidic Solution (强酸性 溶液中에서의 $\beta$-4-Nitroazoxybenzene의 轉位反應에 關한 反應速度論的 硏究)

  • Han, Chi-Sun;Lee, Kwi-Ja;Nam Goong, Ha-Il
    • Journal of the Korean Chemical Society
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    • v.11 no.4
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    • pp.173-178
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    • 1967
  • The rearrangement of ${\beta}$-4-nitroazoxybenzene into 4-hydroxy-4'-nitroazobenzene in strongly acidic solutions has been as certained by UV spectrophotometry. The kinetics of the rearrangement in 20 vol. % ethanol and 80 vol. % of aqueous sulfuric acid-water solutions has been studied, and the rearrangement was found to be acid catalyzed pseudo-frst-order reaction. The mechanism of the rearrangement is also discussed.

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Spectral Study on the Alkaline Hydrolysis of Some Cyano Substituted 4-Amino-4노-Nitroazobenzene Dyes (시아노기 치환 4-아미노-4노-니트로아조벤젠계 염료의 알칼리 가수분해에 대한 분광학적 고찰)

  • 박건용;김진우
    • Textile Science and Engineering
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    • v.28 no.11
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    • pp.63-75
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    • 1991
  • The alkaline hydrolysis behaviors of six two disperse dyes, especially for cyans substituted 4-amino-4'-nitroazobenzene dyes were studied. The dyes containing two ortho substituents in acceptor ring were very rapidly hydrolyzed by alkali and showed both large hypsochromic and hypochromic shifts. These results may be caused by the decrease of electron-withdrawing power of acceptor and steric hindrance resulted from the hydrolysis of the cyano group and certain cleavages by hydrolysis. Similarly for the dyes which have an o-cyano group in acceptor ring, hypsochromic shifts together with reductions in tinctorial strength were also observed by the alkaline hydrolysis. And only the water-insoluble products remained without hypsochromic shift during hydrolysis participated in dyeing of polyester. The dyes containing an acetoxyalkyl group in terminal amino group produced a bathochromic shift by hydrolysis of acetoxy group. In acetone/sodium hydroxide aqueous solution, the tinctorlal strengths of the dyes without o-cyano group were not reduced, but in dyeing, their dye uptakes were gradually reduced with hydrolysis time. Moreover, most of dyes showed obvious decreases of dye uptakes after washing.

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Thermotropic Liquid Crystalline Behavior of α,ω-Bis(4-nitroazobenzene-4'-carbonyloxy)alkanes (α,ω-비스(4-니트로아조벤젠-4'-카보닐옥시)알칸들의 열방성 액정 거동)

  • Jeong, Seung Yong;Hwang, Dong Jun;Ma, Yung Dae
    • Applied Chemistry for Engineering
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    • v.21 no.2
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    • pp.230-237
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    • 2010
  • A homologous series of linear liquid crystal dimers, ${\alpha},{\omega}$-bis(4-nitroazobenzene-4'-carbonyloxy)alkanes (NATWESn, n = 2~8, 10, the number of methylene units in the spacer) have been synthesized, and the thermal behavior of the series has been investigated. All the dimers formed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This behavior was rationalized in terms of the change in the average shape of the spacer on varing the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of NATWESn were very similar to those of the corresponding ether compounds, while they were significantly different from those of the monomesogenic compounds, 4-{4'-(nitrophenylazo)phenoxy}alkanoyl chlorides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-nitrophenylazo) phenoxycarbonylalkanoyloxy}ethylene]s. The results were discussed in terms of the 'irtual trimer model'by Imrie.

Synthesis and Surface Relief Gratings of Three-Armed Star-Shaped Molecules Bearing 4-(N,N-Diphenyl)Amino-4'-Nitroazobenzene Chromophores

  • Lee, Jung-Eun;Jung, Kyung-Moon;Cho, Min-Ju;Kim, Kyung-Hwan;Choi, Dong-Hoon
    • Macromolecular research
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    • v.16 no.5
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    • pp.434-440
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    • 2008
  • Three-armed, star-shaped molecules containing 4-(N,N-diphenyl)amino-4'-nitroazobenzene chromophores were synthesized to study the diffraction behavior after inscribing surface relief gratings. The two molecules differed in terms of their mode of chromophore attachment to the core. In compound 5, they were bound to the core laterally through alkylene spacers, whereas the chromophores were tethered perpendicularly to the core in compound 4. Although 60 wt% of the polar azobenzene chromophores was comprised of large molecules, no aggregation behavior was observed in the absorption spectra of the thin films. The surface relief gratings were elaborated on the surface of the molecular films by the two-beam interference method. The dynamics of grating formation were studied in terms of the diffraction efficiency using two different film samples made up of two star-shaped molecules. The maximum diffraction efficiency of D-$(ENAZ)_3$, compound 4, was measured to be about 30%, which was significantly high. The mode of chromophore attachment affected the dynamic properties of the diffraction gratings.

Self-Crosslinkable Side-Chain Copolymer for Nonlinear Optical Application

  • 한관수;박승구;심상연;장웅상;김낙중
    • Bulletin of the Korean Chemical Society
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    • v.19 no.11
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    • pp.1165-1168
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    • 1998
  • 2-Tetrahydropyranyl methacrylate with a self-crosslinkable moiety was copolymerized with methyl methacrylate and 4-[(2-methacryloxyethyl)methylamino]-4'-nitrostilbene or 4-[(2-methacryloxyethyl)ethylamino]-4'nitroazobenzene to provide second-order nonlinear optical property. Glass transition temperatures (Tg of the copolymers are around 140 ℃. The copolymers were soluble in common organic solvents such as tetrahydrofuran (THF), cyclohexanone, and N,N-dimethylformamide (DMF). Poling was carried out at 140 ℃ for 20 min and identified with UV-Vis spectroscopy. Electro-optic coefficient (r33) of copolymer was 62 pm/V for polymer 2 at 633 nm, and relaxation did not remarkably occur due to the formation of a crosslinked network at 200 ℃ for 15 min.

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Thermotropic Liquid Crystalline Behavior of Hydroxypropyl Celluloses Bearing Cholesteryl and Nitroazobenzene Groups (콜레스테릴과 니트로아조벤젠 그룹을 지닌 히드록시프로필 셀룰로오스들의 열방성 액정 거동)

  • Jeong, Seung-Yong;Ma, Yung-Dae
    • Polymer Korea
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    • v.32 no.5
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    • pp.446-457
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    • 2008
  • Three kinds of hydroxypropyl cellulose (HPC) derivatives: 6- (cholesteryloxycarbonyl) pentoxypropyl celluloses(CHPCs) with degree of esterification(DE) ranging from 0.6 to 3, 6-[4-{4'-(nitrophenylazo)phenoxycarbonyl}] pentoxypropyl celluloses (NHPCs) with DE ranging from 0.4 to 3, and fully 6-(cholesteryloxycarbonyl) pentanoated NHPCs (CNHPCs) were synthesized, and their thermotropic liquid crystalline properties were investigated. All the CHPCs and NHPCs with $DE{\leq}1.7$ formed enantiotropic cholesteric phases, whereas CNHPCs with 6-(cholesteryloxycarbonyl) pentanoyl DE(DEC) more than 1.6 exhibited monotropic cholesteric phases. On the other hand, NHPCs with $DE{\geq}2.4$ and CNHPCs with $DEC{\leq}1.3$ showed monotropic nematic phases. NHPCs with $DE{\leq}l$, as well as HPC, formed right-handed helices whose optical pitches (${{\lambda}_m}'s$) increase with temperature, while all the CHPCs formed left-handed helices whose ${{\lambda}_m}'s$ decrease with temperature. In contrast with these derivatives, NHPCs with $1.4{\leq}DE{\leq}1.7$ and CNHPCs with $DEC{\geq}1.6$ did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cellulose chain and the cholesteryl group highly depends on the chemical structure and DE of mesogenic group.

Thermotropic Liquid Crystalline Behaviors of 4-{4'-(nitrophenylazo)phenoxy}alkanoic Acids and 4-{4'-(nitrophenylazo)phenoxy}alkanoyl Chlorides (4-{4'-(니트로페닐아조)펜옥시}알칸 산들 그리고 4-{4'-(니트로페닐아조)펜옥시}알카노일 클로라이드들의 열방성 액정 거동)

  • Jeong, Seung Yong;Ma, Yung Dae
    • Applied Chemistry for Engineering
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    • v.19 no.5
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    • pp.504-511
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    • 2008
  • Two kinds of nitroazobenzene derivatives: 4-{4'-(nitrophenylazo)phenoxy}alkanoic acids (NAAn, n = 2~8, 10, number of methylene units in the alkyl chain) and 4-{4'-(nitrophenylazo)phenoxy}alkanoyl chlorides (NACn, n = 2~8, 10) were synthesized, and their thermotropic liquid crystalline behaviors were investigated. NAA6 formed an enantiotropic nematic phase, while the remainders, except NAA2, showed monotropic nematic phases. Isotropic-nematic transition temperature ($T_{iN}$) and change of entropy (${\Delta}S$) at $T_{iN}$ for both of NAAn and NACn varied by the change of n, and pronounced odd-even effects of n were also observed. However, the $T_{iN}$ and ${\Delta}S$ values of NAAn were much higher than those of NACn. This fact may be attributed to the hydrogen bonding between carboxyl groups. Thermal properties and degree of order in the mesophase and the magnitude of the odd-even effects of both NAAn and NACn were significantly different from those reported for 4-(alkoxy)-4'-nitroazobenzenes. It was discussed in terms of the differences in the molecular anisotropy and the temperature-dependent flexibility of the substituted groups.

Synthesis and Thermotropic Liquid Crystalline Behaviors of 6-[4-(4'-(nitrophenylazo) phenoxycarbonyl)] pentanoated Polysaccharides (6-[4-(4'-(니트로페닐아조)펜옥시카보닐)]펜타노화 다당류들의 합성과 열방성 액정 거동)

  • Jeong, Seung-Yong;Ma, Yung-Dae
    • Polymer Korea
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    • v.31 no.1
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    • pp.37-46
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    • 2007
  • Fully or nearly fully 6- [4- (4'- (nitrophenylazo)phenoxycarbonyl)]pentanoated polysaccharide derivatives were synthesized by reacting cellulose, amylose, chitosan, chitin, alginic acid, pullulan or amylopectin with 6- [4- (4'- (nitrophenylazo)phenoxy) ] pentanoyl chloride (NA6C) and their thermotropic liquid crystalline behaviors were investigated. Like in the case of NA6C, all the polysaccharide derivatives formed monotropic nematic phases, suggesting that the mesophase structure of the polysaccharide derivatives is dertermined by the mesogenic side groups and not by the polysaccharide backbone. This is the first report of polysaccharide derivatives, except cellulose derivative, that form thermotropic nematic phases. The thermal stability and degree of order of the nematic phases observed for poly saccharide derivatives were significantly different from those reported for the polymers in which the azobenzene groups are attached to flexible or rigid backbones through flexible spacers. The results were discussed in terms of the difference in the arrangement of the main and side chains and the flexibility of the main chain.

Thermotropic Liquid Crystalline Behavior of [4-{4'-(Nitrophenylazo)phenoxycarbonyl}]alkanoated Celluloses ([4-{4'-(니트로페닐아조)펜옥시카보닐}]알카노화 셀룰로오스들의 열방성 액정 거동)

  • Jeong, Seung-Yong;Ma, Yung-Dae
    • Polymer Korea
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    • v.33 no.1
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    • pp.58-66
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    • 2009
  • The thermotropic liquid crystalline behavior of the homologous series of cellulose tri[4-{4'-(nitrophenylazo) phenoxycarbonyl}] alkanoates (NACEn, n=2$\sim$8, 10, the number of methylene units in the spacer) have been investigated. All of the homologoues formed monotropic nematic phases. The isotropic-nematic transition temperature ($T_{iN}$) decreased when n is increased up to 7, but it became almost constant when n is more than 7. The plot of transition entropy at $T_{iN}$ against n had a sharp negative inflection at n=7. The sharp change at n=7 may be attributed to the difference in arrangement of the side groups. The melting temperature ($T_m$) and associated entropy change at $T_m$, in contrast with $T_{iN}$ and associated entropy change at $T_{iN}$, exhibited a distinct odd-even effect, suggesting that the average shape of the side chains in the crystalline phase is different from that in the nematic phase. The thermal stability and degree of order of the nematic phase observed for NACEn were significantly different from those reported for the homologous series of side-chain and combined type liquid crystal polymers bearing azobenzene or biphenyl units in the side chains. The results were discussed in terms of the differences in the chemical structure, the flexibility of the main chain, the mode of chemical linkage of the side group with the main chain, and the number of the mesogenic units per repeating unit.