Competition of Self-Organization and Photo-Orientation in Liquid Crystalline Polymers

Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications

Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photochromism, liquid crystallinity, and fabrication techniques has enabled some fascinating functional materials which can be driven by ultraviolet, visible, and infrared light irradiation. Nanoscale particles have been incorporated to widen and diversify the scope of the light-driven liquid crystalline materials. The developed materials possess huge potential for applications in optics, photonics, adaptive materials, nanotechnology, etc. The challenges and opportunities in this area are discussed at the end of the Review.

New Soluble Polyimides Containing the Hydroxylic Group. II: Polymers Substituted with Disperse Red 1

A series of aromatic polyimides synthesized from various diamidedianhydrides and 2,4-diamino-phenol dihydrochloride were substituted with 4-[N-ethyl-N-(2-hydroxyethyI)Iamino-4'-nitro-azobenzene (Disperse Red 1) via the Mitsunobu reaction. The content of the chromophore in the polyimides has been detenrnined by UV-Vis spectroscopy. The influence of the polyimide structure on the ability for the introduction of the chromophore into the polymers was investigated. Different conditions of the Mitsunobu reaction have enabled the synthesis of polyimides with various contents of DR 1. The induction of optical anisotropy in films of the photochromic polymers was studied by irradiating with the linearly polarized light of an Ar+ laser (488 nm). A dichroism up to 0.2 was induced depending on the content of the push-pull substituted azobenzene side group in these polyimides.