Photomechanical Bending of Azobenzene-Based Photochromic Molecular Fibers

Abstract

Microfibers composed of azobenzene-based photochromic amorphous molecular materials, namely low molecular-mass photochromic materials with a glass-forming property, could be fabricated. These fibers were found to exhibit mechanical bending motion upon irradiation with a laser beam. In addition, the bending direction could be controlled by altering the polarization direction of the irradiated light without changing the position of the light source or the wavelength of the light. In-situ fluorescence observation of mass transport induced at the surface of the fiber doped with CdSe quantum dots suggested that the bending motions were related with the photoinduced mass transport taking place near the irradiated surface of the fiber.

Photoinduced change in the shape of azobenzene-based molecular glass particles fixed in agar gel

“…6 We have been performing studies of the creation of photochromic molecular glasses, namely amorphous glasses of photochromic materials based on low molecular-mass derivatives, 7-9 and in due course we have found several kinds of their photomechanical behaviours related with photoinduced mass transport. They include photo-induced SRG formation on their amorphous films, 9,10 photomechanical bending motion of the molecular fibres of which the bending direction depended upon polarization direction of the incident beam, 11 photoinduced mass flow at the surface of the amorphous films 12 and photoinduced movements of the glass fragments on the substrate. 12,13 These phenomena could be explained by anisotropic mass transport induced in the direction parallel to the polarization direction of incident laser beam.…”

Light-driven bending of diarylethene mixed crystals

“…The photoinduced contraction of liquid-crystal elastomers 5 a is attributed to an order–disorder transition of the liquid-crystal material. The photomechanical bending of amorphous microfibers made of azobenzene derivatives 7 is related to photoinduced mass transport near the irradiated surfaces of the fibers. It is a challenge to construct molecular systems that perform macroscopic mechanical work based on photostimulated geometrical structure or shape changes of individual molecules.…”

“…The movement was, however, too subtle to be put to practical use. On the other hand, various types of polymers, 5 polymer brushes, 6 amorphous microfibers, 7 and carbon nanotubes 8 have been reported to convert molecular phenomena into macroscopic motion of materials. The motion, however, relies not on the individual molecular behaviour but on the response of bulk materials.…”

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

“…Relationship between molecular structures and SRG forming properties have been investigated and it was concluded that the glass-transition temperatures (Tgs) and photochromic reactivity of the materials play an important role for photoinduced SRG formation observed for the azobenzene-based photochromic amorphous molecular materials [22][23][24]. Not only photoinduced SRG formation but also other photomechanical behaviors have been found including photomechanical bending motions azobenzene-based amorphous molecular fibers depending upon the polarization direction of incident beam [25,26], photoinduced mass flow at the surface of the azobenzene-based amorphous molecular films by angled irradiation with ppolarized laser beam [27], photoinduced movements of the glass fragments of the azobenzene-based amorphous molecular materials by angled irradiation with p-polarized laser beam from the bottom [27,28], photoinduced changed in phase-separated structures of composite films of azobenzene-based amorphous molecular materials together with poly(vinyl acetate) [29,30], and photoinduced structural changes of the glass particles of azobenzene-based amorphous molecular materials fixed in agar gel [31,32]. All these phenomena could be explained by the photoinduced vibration and/or transport of molecules parallel to the polarization direction of the incident beam.…”