Photofabrication of Surface Relief Grating on Films of Azobenzene Polymer with Different Dye Functionalization

Abstract

Photofabrication of surface relief grating (SRG) on very high-Tg and lower-Tg azobenzene functionalized polymers was investigated. Polymers with different degrees of functionalization were designed and synthesized to understand the chemical and physical intricacies involved at the molecular level in the photofabrication of SRG. The systematic study examined the influence of three important parameters: the degree of azo functionalization, the irradiating light intensity, and the initial film thickness. From the experimental results, we establish that the writing behavior of photofabricated SRG depends on the degree of azo functionalization. The effective critical intensity of the irradiating light was found to be independent of the degree of functionalization. Threshold behavior for the deformation process as a function of the degree of functionalization was established. The observed film thickness dependence of the SRG formation is discussed within the framework of existing fluid mechanics model. The thermal properties of the photofabricated SRG were also investigated.

Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

“…The stability can be improved when one employs amorphous polymers with high T g 114,115 or liquid crystalline polymers having high T i (transition temperature to isotropic state). 116 However, high T g or T i materials severely reduce the mass mobility.…”

“…The process employed here can be compared with a simple approach using Az polymers of high T g . Fukuda et al 114,115 employed maleimide-based high T g amorphous polymer (T g ¼ 170{279 C). In their polymer systems, the thermal stability is considerably improved, however, in compensation for requirement of vast amounts of exposure energy.…”

Light-Triggered Formation of Surface Topographies in Azo Polymers

“…This light-induced realignment process creates typical SRG topographies with the maxima located in the low intensity regions of the intensity interference pattern. This is observed for azo-containing polymers, even with high glass transition temperatures [43]. linear polymers containing this photosensitive molecule, it is necessary to incorporate the dye via (non-)covalent bonds to the polymer (via side or main chain or hydrogen bonding).…”

Optical and Physical Applications of Photocontrollable Materials: Azobenzene-Containing and Liquid Crystalline Polymers

“…Using this method, the spacing of periodic structures can be varied in practice from 0.3 to 50 μm (or more) by just adjusting a coupling angle of the two coherent beams. The PSR inscription rate depends on many experimental parameters such as the value of the spacing, the initial film thickness, and the azobenzene functionalization [116,117].…”