Photorefractive triphenylamine-based glass: a multifunctional low molecular weight compound with fast holographic response

Hohle, Christoph; Hofmann, Uwe; Schloter, Stefan; Thelakkat, Mukundan; Strohriegl, Peter; Haarer, D.; Zilker, Stephan J.

doi:10.1039/a902562f

Cited by 47 publications

(26 citation statements)

References 13 publications

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“…[3] One disadvantage of this material is that aluminum borate whiskers will react with matrices, and thus decrease the tensile strength of composites significantly. [5,6] Boron nitride is a chemically inert and thermally resistant material, and BN nanotubes have been widely researched.…”

Section: Methodsmentioning

confidence: 99%

Undoped Photorefractive Ferroelectric Liquid Crystal

et al. 2003

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Light-sensitive media constitute a class of materials that are extensively studied because of their technological relevance for a variety of applications. In particular, the non-local reversible refractive index control by light, which is possible in substances exhibiting photorefractive properties, is of wide interest for real-time holography.[1] Photorefractivity is observed in photoconductors when a spacially non-uniform light exposure generates charge carriers which redistribute over macroscopic distances. This causes an electric field, which affects the refractive index of the material. Driven by the aim of obtaining low-cost and easily processable media, many efforts have been devoted to the understanding of the photorefractive properties of organic amorphous glasses [2±4] and polymers, [5±9] followed more recently by the interest in photorefractive liquid crystals. [10] Mesophases are attractive for photorefractivity because of their high spontaneous birefringence and the wide variety of field-induced refractive index control mechanisms.[11] The first liquid crystals studied for their photorefractive properties were bulk [12±14] and dispersed [15,16] nematic materials, but in the last years a number of investigations have showed that smectic phases can be photorefractive as well. [17±19] In particular, studies were carried out on chiral smectic A and C phases, where the mechanisms of field-induced fast molecular reorientation are connected with an induced or permanent polarization, respectively. [20] In all the reported investigations, the liquid-crystalline phase is not intrinsically photoconducting, so that the space±charge field set up is achieved either by dissolving a light sensitizer (and often a charge-transport agent as well) within its bulk, or by placing the mesophase within (like in dispersed systems), or between layers of, a photoconducting material. In this work the first example of a smectic mesophase that exhibits photorefractive behavior without any doping will be presented. It will also be shown that the observed photorefractive performance is larger than that previously reported for doped systems. Our approach is based on two recent results: the observation of photorefractivity in amorphous glasses formed by cyclopalladated complexes [21] and the synthesis of a new complex, with a closely related molecular structure, which exhibits a chiral smectic C phase. [22] The mesomorphic behavior of this complex, with a structure shown in Figure 1a and called for simplicity AzPdL, was investigated by optical microscopy, differential scanning calorimetry (DSC) and low-angle X-ray diffraction measurements. The observed transition temperatures between the isotropic (I), cholesteric (N*), chiral smectic C (SmC*) and crystalline (Cr) phases are included in Figure 1a.

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Section: Methodsmentioning

confidence: 99%

Undoped Photorefractive Ferroelectric Liquid Crystal

et al. 2003

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“…[31][32][33][34][35][36][37][38] Azobenzenes of donor-acceptor type have been found to form characteristic aggregates depending on the solvent composition, polarity, and the solute concentration. Studies directed towards aggregation of azobenzenes have mainly concentrated on: 1) simpler azobenzene molecular entities of donor-acceptor and electronically symmetric type; [39,40] 2) surfactant-like azobenzene derivatives functionalized with long alkyl chains and apexed with a polar head group; [41,42] and 3) azo moieties with polar or nonpolar head groups, appended as side chains on polymeric backbones. [43,44] With the aim of developing photomodulated phthalocyanine J-aggregates, a-aryl/ alkoxy-substituted zinc phthalocyanine dyads (3-azo-ZnPc and 4-azo-ZnPc) have been synthesized by LiHong Niu et al [45] In noncoordinating solvents, the 3-azo-ZnPc could be effectively photocontrolled as a result of changes in the geometry and dipole moment of azobenzene on the dyad framework.…”

Section: Introductionmentioning

confidence: 99%

Solvent‐Polarity‐Tunable Dimeric Association of a Fullerene (C₆₀)–N,N‐Dimethylaminoazobenzene Dyad: Modulated Electronic Coupling of the Azo Chromophore with a Substituted 3D Fullerene

Kumar

Patnaik

2011

Chemistry A European J

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The tunable self-assembly of a fullerene (C(60))-N,N-dimethylaminoazobenzene (DPNME) molecular system as a function of solvent polarity in THF/water binary solvent is reported. Gradual increase of the volume fraction of the nonsolvent water in a 1×10(-5) M THF solution of DPNME at a mixed dielectric constant ε(mix)≈42 resulted in initial redshifting of the (1)(π→π(*)) absorption band, which signified the 1D head-to-tail or J-type arrangement of the DPNME molecular system. Further increase in the solvent polarity to ε(mix)≈66 evidenced formation of an antiparallel head-to-tail or H-type molecular arrangement in conjunction with the J-aggregates, thereby establishing a solvent-polarity-dependent dynamic equilibrium between the monomer ↔ J-aggregate ↔ H-aggregate. The controlled aggregation was governed by the synergetic effect of intermolecular donor-acceptor interaction between the electron-deficient fullerene ring and the electron-rich N,N-dimethylamino-substituted aromatic ring; typically, van der Waals and π-π interactions between the molecules constituting a pair of dimers were envisaged. An agreement between the semiempirically calculated drastically reduced oscillator strength of the DPNME H-dimer in the antiparallel configuration (0.69 vs. 1.29 in the monomeric DPNME) and the experimental electronic absorption spectra beyond ε(mix)=66 further strengthened this assignment to the hitherto forbidden antiparallel H-dimer. Complementing the above, the periodicity of molecular self-assembly dictated a monoclinic unit cell in the single-crystal XRD packing pattern with a C2/c space group; the molecules packed laterally with mutual interdigitation with the donor (E)-N,N-dimethyl-4-(p-tolyldiazenyl)aniline (AZNME) parts in an antiparallel fashion (contrary to the usual expectation for H-aggregates) with strong inter- and intrapair van der Waals and π-π interactions between the constituent fullerene moieties. Unlike those of porphyrin/phthalocyanine bowl-like donor-initiated architectures, a rare class of DPNME dyadic supramolecular self-assemblies was realized with π-extended 2D fullerene networks, in which the linear geometry of the AZNME donor and the conformational rigidity of the fullerene acceptor played crucial roles.

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“…[33,34] As photoconductive or multifunctional materials they can be applied in photorefractive systems. [35] Molecular glasses are also candidates for the application as electrically conducting materials, [13] photochromic materials, [36,37] and resist materials for electron-beam lithography. [38] Low molar mass organic materials with a liquid crystalline order that are stable in the glassy state can be applied for rewritable full-color recording in a photon mode, [39] and photopolymerizable liquid-crystalline glass-forming molecular materials can be used for the preparation of cholesteric crosslinked pigments for effect paints.…”

Section: Introductionmentioning

confidence: 99%

Charge-Transporting Molecular Glasses

Strohriegl¹,

2002

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Among organic materials vitrification for many years was regarded mainly as a privilege of polymers. However, recently a lot of attention is paid to organic low molar mass compounds that readily form glasses above room temperature. Such compounds are called molecular glasses or amorphous molecular materials. Among these materials the most widely studied are charge‐transporting molecular glasses used in copiers and laser printers, organic light‐emitting diodes, photovoltaic devices, and as photorefractive materials. Two types of molecular glasses, i.e., p‐type (hole‐transporting), and n‐type (electron‐transporting) are discussed. Work of the laboratories of the authors is emphasized. In addition, an overview of current and potential applications for these materials is presented.

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Photorefractive triphenylamine-based glass: a multifunctional low molecular weight compound with fast holographic response

Cited by 47 publications

References 13 publications

Undoped Photorefractive Ferroelectric Liquid Crystal

Undoped Photorefractive Ferroelectric Liquid Crystal

Solvent‐Polarity‐Tunable Dimeric Association of a Fullerene (C₆₀)–N,N‐Dimethylaminoazobenzene Dyad: Modulated Electronic Coupling of the Azo Chromophore with a Substituted 3D Fullerene

Charge-Transporting Molecular Glasses

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Photorefractive triphenylamine-based glass: a multifunctional low molecular weight compound with fast holographic response

Cited by 47 publications

References 13 publications

Undoped Photorefractive Ferroelectric Liquid Crystal

Undoped Photorefractive Ferroelectric Liquid Crystal

Solvent‐Polarity‐Tunable Dimeric Association of a Fullerene (C60)–N,N‐Dimethylaminoazobenzene Dyad: Modulated Electronic Coupling of the Azo Chromophore with a Substituted 3D Fullerene

Charge-Transporting Molecular Glasses

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Solvent‐Polarity‐Tunable Dimeric Association of a Fullerene (C₆₀)–N,N‐Dimethylaminoazobenzene Dyad: Modulated Electronic Coupling of the Azo Chromophore with a Substituted 3D Fullerene