Photochromic Amorphous Molecular Materials. Synthesis and Photochromic Properties of a New Azobenzene Derivative, 4-(Bls(4-methylphenyl)amino)-4'-methoxyazobenzene.

Abstract

Low molecular-weight organic compounds generally tend to crystallize readily. We have been performing studies of the creation of low molecular-weight organic compounds that readily form stable amorphous glasses above room temperature, which we refer to as amorphous molecular materials, and investigating their structures, reactions, properties, and applications. [1][2][3][4][5] As a part of these studies, we have studying the creation of low molecular-weight organic photochromic compounds that readily form stable amorphous glasses above room temperature, which we refer to as "photochromic amorphous molecular materials". These compounds may constitute a novel family of photochromic materials that form uniform amorphous thin films by themselves. These materials have an advantage that there is no dilution of photochromic chromophores relative to photochromic polymers and composite polymer systems, where low molecular-weight photochromic compounds may crystallize at high concentration. Based on this new concept, we have designed and synthesized 4-[bis(4-methylphenyl)amino]azobenzene (BMAB) and 4-di(biphenyl-4-yl)aminoazobenzene (DBAB). [6,7] These compounds readily form amorphous glasses with glasstransition temperatures (Tgs) of 27 and 68 °C, respectively, and exhibit photochromism in their amorphous films. It has been found that the fraction of cis-isomer at the photostationary state is smaller in their amorphous films than in the solution. The result indicates that the local free volume is not large enough to allow all the molecules to isomerize from the trans-form to the cis-form in the amorphous film.It is thought that the fraction of cis-isomer at the photostationary state depends on both the size and distribution of local free volume and the volume needed for isomerization from the transisomer to the cis-isomer. In the present study, we have synthesized a new azobenzene derivative, 4-[bis(4-methylpheny)amino]-4'-methoxyazobenzene (MeO-BMAB), and investigated its photochromic behavior in comparison with those of BMAB and DBAB in order to gain information about the relationship between the molecular structure and the fraction of cis-isomer at the photostationary state.The new compound, MeO-BMAB, was found to form readily an amorphous glass when the melt

Photo- and electroactive amorphous molecular materials—molecular design, syntheses, reactions, properties, and applications

“…11,[28][29][30][31][32][33] The synthesised azobenzene-based compounds include 4-[bis(4-methylphenyl)amino]azobenzene (BMAB), 4-[bis(4-methylphenyl)amino]-49-methoxyazobenzene (MeO-BMAB), 4-[di(biphenyl-4-yl)amino]azobenzene (DBAB), 4-[bis (9,9-dimethylfluoren-2-yl)amino]azobenzene (BFlAB), 4-[ bis ( 9, 9 -dimethylfluoren -2 -yl) amino ] -49-nitroazobenzene (BFlAB-NO 2 ), 4,49-bis[bis(4-methylphenyl)amino]azobenzene (BBMAB), and 4,49-bis[bis(49-tert-butylbiphenyl-4-yl)amino]-azobenzene (t-BuBBAB). 11,28,29,32,33 BFlAB was synthesised by the Ullmann coupling reaction of 4-aminoazobenzene with 2-iodo-9,9-dimethylfluorene.…”

“…Considering that the photochromic behaviour of azobenzenes have been studied extensively and that dithienylethenes are known as fatigue-resistant, thermally stable photochromic compounds, we have created photochromic amorphous molecular materials based on azobenzene and dithienylethene chromophores. 11,[28][29][30][31][32][33] 30,31 All these compounds readily formed amorphous glasses with well-defined T g s when the melt samples were cooled on standing in air. T g increased with the increasing molecular size, with the introduction of rigid moieties, e.g., biphenyl and fluorenyl groups, and with the introduction of polar substituents.…”

Photomechanical Behaviors of Azobenzene-based Amorphous Molecular Materials: Photoinduced Structural Changes of Amorphous Films of 4-[Bis(9,9-dimethylfluoren-2-yl)amino]azobenzene Analogues Fabricated on the Surface of Agar Gel

“…We have performing studies on the creation of low molecular-mass photochromic materials that readily form amorphous glasses, namely photochromic amorphous molecular materials [14][15][16][17][18][19][20] and in due course, we have found that azobenzene-based photochromic amorphous molecular materials exhibited several unique photomechanical behaviors related to photoinduced mass transport. At the initial stage, photoinduced SRG formation taking place for amorphous film of 4-[bis(9,9-dimethylfluoren-2-yl]aminoazobenzene (BFlAB) was observed upon irradiation with coherent laser beams [21].…”

Photoinduced Shape Changes of Mixed Molecular Glass Particles Containing Azobenzene-Based Photochromic Amorphous Molecular Materials Fixed in Agar Gel

“…The authors have performed several parts of a series of studies on creation of amorphous molecular materials, namely low-molecular-mass organic materials that readily form amorphous glasses at temperatures above room temperature. − We have later created photochromic amorphous molecular materials and investigated their photochromic reaction properties in their amorphous states. − In addition, we have found that azobenzene-based photochromic amorphous molecular materials exhibited several kinds of photomechanical behaviors related to photoinduced mass transport. − For example, it has been demonstrated that SRG formation of azobenzene-based amorphous molecular materials is induced by coherent irradiation of laser beams and that the SRG forming ability depends upon the polarization direction of the incident beams, p-polarized beams being preferable to s-polarized ones. − , Subsequently, we have fabricated molecular fibers of azobenzene-based amorphous molecular materials by the melt-spinning method, and the fibers exhibited photoinduced bending motions. Interestingly, the bending direction of the fibers could be controlled by altering the polarization direction of the incident beams, that is, polarized beams with polarization directions parallel and perpendicular to the fiber axis induced bending in the direction opposite and toward the light source, respectively. , In addition, we have demonstrated photoinduced mass flow on the surface of amorphous films and photoinduced movements of glass fragments placed on the substrate upon angled irradiation of the p-polarized laser beam. , These phenomena were also found to depend upon polarization direction of the incident beam, s-polarized beam being unable to induce such phenomena.…”