title: Stable holographic gratings with small-molecular trisazobenzene derivatives.
abstract: 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.
authors.affiliation: Macromolecular Chemistry I, University of Bayreuth, D-95440 Bayreuth, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Kreger
authors.forename: Pascal
authors.initials: P
authors.lastname: Wolfer
authors.forename: Hubert
authors.initials: H
authors.lastname: Audorff
authors.forename: Lothar
authors.initials: L
authors.lastname: Kador
authors.forename: Natalie
authors.initials: N
authors.lastname: Stingelin-Stutzmann
authors.forename: Paul
authors.initials: P
authors.lastname: Smith
authors.forename: Hans-Werner
authors.initials: HW
authors.lastname: Schmidt
mesh_terms: D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008567:Membranes, Artificial; D015394:Molecular Structure; D008970:Molecular Weight; D013696:Temperature; D013997:Time Factors
chemical_list: D001391:Azo Compounds; D008567:Membranes, Artificial; C009850:azobenzene