Stable holographic gratings with small-molecular trisazobenzene derivatives.
We present a series of small-molecular trisazobenzene chromophores, including, for instance, 1,3,5-tris{[4-[4-[(4-cyanophenyl)azo]phenoxy]butyryl]amino}benzene that feature a remarkably stable light-induced orientation in initially amorphous thin-film architectures. It is demonstrated that for optimal performance it is critical to design chemical structures that allow formation of both an amorphous and a liquid-crystalline phase. In the present approach, the liquid-crystalline feature was introduced by inserting decoupling spacers between a trisfunctionalized benzene core and the three azobenzene moieties, as well as adding polar end groups to the latter. To compensate for the deleterious reduction of the glass transition temperature associated with the spacers in the compounds, polar units were incorporated between the benzene core and the side groups. Intriguingly, the molecular glasses that feature a latent liquid-crystalline phase display a remarkable "postdevelopment", i.e., an increase of the amplitude of refractive index modulation in holographic experiments after writing of optical gratings is arrested, exceeding 20% for the previously mentioned derivative. Thus, these nonpolymeric, azobenzene-containing compounds presented in this work appear to be attractive candidates for fabrication of stable holographic volume gratings.
Kreger
Klaus
K
Macromolecular Chemistry I, University of Bayreuth, D-95440 Bayreuth, Germany.
Wolfer
Pascal
P
Audorff
Hubert
H
Kador
Lothar
L
Stingelin-Stutzmann
Natalie
N
Smith
Paul
P
Schmidt
Hans-Werner
HW
D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008567:Membranes, Artificial; D015394:Molecular Structure; D008970:Molecular Weight; D013696:Temperature; D013997:Time Factors
D001391:Azo Compounds; D008567:Membranes, Artificial; C009850:azobenzene