Liquid crystals are promising materials for optical switching and image storage because of their high resolution and sensitivity. Azobenzene liquid crystals (LCs) have been developed, in which azobenzene moieties play roles as both mesogens and photosensitive chromophores. Azobenzene LC films showed a nematic phase in trans isomers and no LC phase in cis isomers. Trans-cis photoisomerization of azobenzene with a laser pulse resulted in a nematic-to-isotropic phase transition with a rapid optical response of 200 microseconds.

http://science.sciencemag.org/content/sci/268/5219/1873.full.pdf

Optical Switching and Image Storage by Means of Azobenzene Liquid-Crystal Films

Physical aging of polymers

Polymers for gas separations: the next decade

All optical fabrication of Surface Relief Grating (SRG) on azobenzene functionalized polymer films is reviewed in this article. The uniqueness of the single step erasable photofabrication of large amplitude surface relief structures on azo polymer films is mainly due to the photoisomerization and photoanisotropic behavior of the azobenzene group. The design and synthesis of several classes of suitable azobenzene functionalized polymers for the SRG formation is presented. Experimental studies are carried out in a systematic manner to understand the chemical and physical intricacies involved in the SRG formation process. Structural requirements and their limitations for the efficient fabrication of SRGs on azo functionalized polymer films are also discussed. Understanding the fundamental mechanism of SRG formation on the azo functionalized polymer films enables us to make use of these structures in a variety of applications.

Surface relief structures on azo polymer films

Positron annihilation spectroscopy for chemical analysis: A novel probe for microstructural analysis of polymers☆

Etude sur le polystyrene. Technique basee sur l'isomerisation photochimique des marqueurs photochroniques et fluorescents

On measuring the distribution of local free volume in glassy polymers by photochromic and fluorescence techniques

Photochromic and fluorescent probe studies in glassy polymer matrices. 3. Effects of physical aging and molar weight on the size distribution of local free volume in polystyrene

It is found that physical ageing in PMMA decreases the isomerization ability of probes requiring larger volumes to isomerize more than the probes that require smaller volumes. The results indicate that, upon physical aging, larger pockets ol local free volume decrease in number more than the smaller pockets, causing the size distribution of local free volume to narrow upon aging. The degree of the decrease in a local free volume fraction was found to depend on the aging time and aging temperature.

Photochromic and fluorescent probe studies in glassy polymer matrices. 4. Effects of physical aging on poly(methyl methacrylate) as sensed by a size distribution of photochromic probes

John G. Victor

Papers

On measuring the distribution of local free volume in glassy polymers by photochromic and fluorescence techniques

Photochromic and fluorescent probe studies in glassy polymer matrices. 3. Effects of physical aging and molar weight on the size distribution of local free volume in polystyrene

Photochromic and fluorescent probe studies in glassy polymer matrices. 4. Effects of physical aging on poly(methyl methacrylate) as sensed by a size distribution of photochromic probes

Photochromic and Fluorescent Probe Studies in Glassy Polymer Matrices. 2. Isomerizable Planar Probe Molecules Lacking an Inversion Center of Symmetry