Dielectric and Photoorientation Studies in Semicrystalline Melamine Monomers and Amorphous Melamine Networks Containing Azobenzene Chromophores

Abstract

We demonstrate optical storage by means of trans-cis isomerization within melamine monomers as well as within the corresponding cross-linked melamine resins using holographic grating experiments. The melamine monomer is chemically linked with a photoaddressable azobenzene group. By thermal treatment the semicrystalline monomers can be converted into the amorphous cross-linked resin. Both the monomer material and the cross-linked resins display a photoinduced trans-cis isomerization of the azo groups, a stable photoorientation under irradiation with linear polarized light, and a stable storage of holographic gratings. The photokinetics in the different environments are found to be similiar but somewhat faster for the amorphous resins.

Influence of chromophore concentration and network structure on the photo‐orientation properties of crosslinked epoxy‐based azopolymers

“…The level of maximum birefringence that can be achieved was about 0.03 (for 24 wt % DO3), which is similar to previously published systems, such as the studies of the photo‐orientation in melamine networks containing DO3 reported by Stracke et al18 There, it was shown that the maximum photoinduced birefringence obtained was 0.034 for materials containing more than 50 wt % chromophore. In a series of papers, Rochon et al19–21 demonstrated that for amorphous polymers containing electron‐donor substituents on the azobenzene group, the maximum variation in refractive index obtained was 0.08.…”

Liquid Crystalline Polymers. 15. Synthesis and Thermal Behavior of Some Aromatic Polyethers Containing Different Spacers

“…For decades work in the area of polymer liquid crystals (PLC) has been extensively carried out due to their valuable applications, such as ultra-high-strength fibers (the best example being Kevlar), electro-optical displays, optical memory systems, dendritic systems and many others [1][2][3][4][5][6][7][8]. Our efforts have been focused on the synthesis and study of new polymers having liquid crystalline properties.…”

“…Special attention was given to the polymers containing azobenzene groups due to their potential application in holographic techniques, as optical memory systems, materials with conformational photo-control, etc. [4][5][6][7][8]. The capacity of azobenzene chromophore to undergo changes in its conformation, from the more thermodynamically stable trans form into the less-favored cis one, under UV radiation was demonstrated [14].…”

Dielectric Analysis (DEA)

“…For example, liquid crystalline sidechain polymers are used for reversible optical data storage and dielectric analysis has been successfully applied for investigating the mechanisms involved in the storage procedure (Stracke et al 2000 ). For example, liquid crystalline sidechain polymers are used for reversible optical data storage and dielectric analysis has been successfully applied for investigating the mechanisms involved in the storage procedure (Stracke et al 2000 ).…”