title: Photochromic hybrid organic-inorganic liquid-crystalline materials built from nonionic surfactants and polyoxometalates: elaboration and structural study.
abstract: This work reports the elaboration and structural study of new hybrid organic-inorganic materials constructed via the coupling of liquid-crystalline nonionic surfactants and polyoxometalates (POMs). X-ray scattering and polarized light microscopy demonstrate that these hybrid materials, highly loaded with POMs (up to 18 wt %), are nanocomposites of liquid-crystalline lamellar structure (Lalpha), with viscoelastic properties close to those of gels. The interpretation of X-ray scattering data strongly suggests that the POMs are located close to the terminal -OH groups of the nonionic surfactants, within the aqueous sublayers. Moreover, these materials exhibit a reversible photochromism associated to the photoreduction of the polyanion. The photoinduced mixed-valence behavior has been characterized through ESR and UV-visible-near-IR spectroscopies that demonstrate the presence of W(V) metal cations and of the characteristic intervalence charge transfer band in the near-IR region, respectively. These hybrid nanocomposites exhibit optical properties that may be useful for applications involving UV-light-sensitive coatings or liquid-crystal-based photochromic switches. From a more fundamental point of view, these hybrid materials should be very helpful models for the study of both the static and dynamic properties of nano-objects confined within soft lamellar structures.
authors.affiliation: Laboratoire de Physique des Solides, Université Paris Sud, CNRS, UMR 8502, F-91405 Orsay Cedex, France.
authors.forename: Andreas S
authors.initials: AS
authors.lastname: Poulos
authors.forename: Doru
authors.initials: D
authors.lastname: Constantin
authors.forename: Patrick
authors.initials: P
authors.lastname: Davidson
authors.forename: Marianne
authors.initials: M
authors.lastname: Impéror
authors.forename: Brigitte
authors.initials: B
authors.lastname: Pansu
authors.forename: Pierre
authors.initials: P
authors.lastname: Panine
authors.forename: Lionel
authors.initials: L
authors.lastname: Nicole
authors.forename: Clément
authors.initials: C
authors.lastname: Sanchez