Photochromic Hybrid Organic−Inorganic Liquid-Crystalline Materials Built from Nonionic Surfactants and Polyoxometalates: Elaboration and Structural Study

• Published in: Langmuir 2008-06, Vol.24 (12), p.6285-6291
• Main Authors: Poulos, Andreas S, Constantin, Doru, Davidson, Patrick, Impéror, Marianne, Pansu, Brigitte, Panine, Pierre, Nicole, Lionel, Sanchez, Clément
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Condensed Matter; Exact sciences and technology; General and physical chemistry; Materials: Nano-and Mesostructured Materials, Polymers, Gels, Liquid Crystals, Composites; Physics; Soft Condensed Matter; Surface physical chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la8004322

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 (Lα), 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 WV 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.