Synthesis and Metal-like Luster of Novel Polyaniline Analogs Containing Azobenzene Unit

Kukino, Minoru; Kuwabara, Junpei; Matsuishi, Kiyoto; Fukuda, Takashi; Kanbara, Takaki

doi:10.1246/cl.2010.1248

Cited by 22 publications

(25 citation statements)

References 38 publications

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“…In the present research, we further find that π -conjugated copolymer 4 (Fig. 1d)2829, consisting of azobenzene and aniline repeating units, also forms well-defined microspheres quantitatively.…”

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confidence: 76%

Self-assembled conjugated polymer spheres as fluorescent microresonators

Tabata

Braam

Kushida

et al. 2014

Sci Rep

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Confinement of light inside an active medium cavity can amplify emission. Whispering gallery mode (WGM) is one of mechanisms that amplifies light effectively by confining it inside high-refractive-index microstructures, where light propagates along the circumference of a sphere via total internal reflection. Here we show that isolated single microspheres of 2–10 μm diameter, formed from self-assembly of π-conjugated alternating copolymers, display WGM photoemission induced by laser pumping. The wavelengths of the emission peaks depend sensitively on the sphere size, position of the excitation spot and refractive index of each polymer. The Q-factor increases with increasing sphere diameter and displays a linear correlation with the reciprocal radius, indicating that the small curvature increases the efficacy of the total internal reflection. WGM photoemission from π-conjugated polymer microspheres is unprecedented and may be of high technological impact since the microspheres fulfill the role of fluorophores, high-refractive-index media and resonators simultaneously, in addition to their simple fabrication process.

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confidence: 76%

Self-assembled conjugated polymer spheres as fluorescent microresonators

Tabata

Braam

Kushida

et al. 2014

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“…According to the previous paper, molecular weight and effective conjugated length of the main‐chain‐type azobenzene polymers influence progress of the photoisomerization . Synthesis of main‐chain‐type azo‐polymer films prepared by Pd‐catalyzed polycondensation having colored surface with metallic luster and its application as a reflective film has been reported . Several phenomena, such as “molecular accordions” showing molecular shrink and elongation repeatedly upon light irradiation and “molecular zippers” having a function of repeat opening and closing, have been reported.…”

Section: Introductionmentioning

confidence: 98%

“…13 Synthesis of main-chain-type azo-polymer films prepared by Pd-catalyzed polycondensation having colored surface with metallic luster and its application as a reflective film has been reported. [14][15][16] Several phenomena, such as "molecular accordions" showing molecular shrink and elongation repeatedly upon light irradiation 17 and "molecular zippers" having a function of repeat opening and closing, 18 have been reported. Biologyrelated researches using azo-polymer have been performed.…”

mentioning

confidence: 99%

Synthesis of methyl‐substituted azobenzene–carbazole conjugated copolymers with photoinduced structural changes

Otaki

Kumai

Goto

2019

J. Polym. Sci. Part A: Polym. Chem.

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Azobenzene switches its structure instantaneously by reversible trans‐to‐cis and cis‐to‐trans photoisomerization with light irradiations. Dynamic change in polymer structure is expected via introducing an azobenzene unit into the main chain. In this study, a set of methyl‐substituted azobenzene–carbazole conjugated copolymers is synthesized by the Suzuki–Miyaura coupling method. Introduction of methyl substituents to the azobenzene unit of the monomer, and polymerization in a high‐boiling solvent improve the molecular weight of the polymer. Decrease of effective conjugation length due to the twisted structure of the main chain allows progress of photoisomerization. The microstructure of the polymer was determined with grazing incidence X‐ray diffraction (GIXD) measurements using synchrotron radiation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1756–1764

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“…25−31 However, one drawback of the fluorescent microresonators we reported is attributed to the low intrinsic photoemission properties of the copolymers, which exhibit an absolute fluorescent quantum yield (ϕ FL ) of less than 0.02 in their solid state. 19,32,33 In this article, we focus our attention on isolated conjugated polymers (ICPs). 34−40 Most ICPs show high ϕ FL even in the solid state because their π-conjugated main chains are highly isolated from one another by insulating cyclic side chains.…”

Section: ■ Introductionmentioning

confidence: 99%

Whispering Gallery Resonance from Self-Assembled Microspheres of Highly Fluorescent Isolated Conjugated Polymers

et al. 2015

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Self-assembly of highly fluorescent isolated conjugated polymers (ICPs), comprising alternating phenylene moieties with an insulating cyclic side chain and different arylene moieties, was comprehensively studied. Two out of nine ICPs were identified to form well-defined spheres of 1−6 μm diameter. The degree of twisting of the main chains was found to be an important structural factor enabling formation of spheres, for which dihedral angles >50°between the neighboring arylene moieties were required. A single microsphere with high sphericity exhibited whispering gallery mode (WGM) photoemission upon excitation with a focused laser. In this emission, sharp and periodic emission lines were superimposed on a broad photoemission spectrum. The WGM spectral profiles were very sensitive to the integrity of the spherical geometries and surface smoothness, which depends on the self-assembling condition as well as the structure of the polymer backbone. Microspherical optical resonators consisting of such highly fluorescent conjugated polymers are novel. They also present advantages in that (i) there is no need for a light waveguide and fluorescent-dye doping, (ii) its high refractive index is beneficial for light confinement, and (iii) the fabrication process is simple, not requiring sophisticated, costly microfabrication technology. ■ INTRODUCTIONπ-Conjugated polymers possess charge transport, photoemission, and redox properties, which are useful for applications in electronic and optoelectronic devices such as light-emitting diodes, transistors, solar cells, and electrochromic devices. 1−6 Recently, spherical colloids formed from π-conjugated polymers have attracted attention for additional optical and biomedical applications involving fluorescence imaging, drug and gene delivery, and colloidal photonic crystals. 7−9 However, in general, π-conjugated polymers are hard to form into well-defined spheres because of their rigid and planar backbones. Thus, there have been few examples of π-conjugated polymer spheres reported so far. 8,10−16 Moreover, most of these were prepared using miniemulsion polymerization and dispersion polymerization methods.In this context, we have recently reported several π-conjugated alternating copolymers that form well-defined microspheres quantitatively via self-assembly in a thermodynamic solution process. 17,18 The slow diffusion of a polar nonsolvent vapor into a solution of a low-crystallinity polymer results in the formation of spheres with diameters in the submicrometer to several micrometers range. Interestingly, upon laser excitation of a single sphere, clear whispering gallery modes (WGM) were observed in photoemission. 19 Because the refractive indices (η) of these polymers are in the range of 1.6− 1.8, which is high enough in comparison with the refractive index of air (η air ∼ 1.0), fluorescence generated inside the microspheres is efficiently confined via total internal reflection at the polymer/air interface. As a result, sharp and periodic emission lines appear in their photolumine...

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Synthesis and Metal-like Luster of Novel Polyaniline Analogs Containing Azobenzene Unit

Abstract: Pd-catalyzed polycondensations of aniline derivatives and 4,4′-dibromoazobenzene afford polyaniline analogs containing an azobenzene unit in good yields. The obtained polymers are red in solution and in thin-film states, whereas they exhibit green metal-like luster in thick-film states.

Cited by 22 publications

References 38 publications

Self-assembled conjugated polymer spheres as fluorescent microresonators

Self-assembled conjugated polymer spheres as fluorescent microresonators

Synthesis of methyl‐substituted azobenzene–carbazole conjugated copolymers with photoinduced structural changes

Whispering Gallery Resonance from Self-Assembled Microspheres of Highly Fluorescent Isolated Conjugated Polymers

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