title: Phototunable liquid-crystalline phases made of nanoparticles.
abstract: The properties of liquid-crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state.
authors.affiliation: Department of Chemistry, University of Warsaw, Al. Zwirki i Wigury 101, 02-089 Warsaw (Poland).
authors.forename: Anna
authors.initials: A
authors.lastname: Zep
authors.forename: Michal M
authors.initials: MM
authors.lastname: Wojcik
authors.forename: Wiktor
authors.initials: W
authors.lastname: Lewandowski
authors.forename: Kaja
authors.initials: K
authors.lastname: Sitkowska
authors.forename: Aleksander
authors.initials: A
authors.lastname: Prominski
authors.forename: Jozef
authors.initials: J
authors.lastname: Mieczkowski
authors.forename: Damian
authors.initials: D
authors.lastname: Pociecha
authors.forename: Ewa
authors.initials: E
authors.lastname: Gorecka
keywords: azo compounds; isomerization; liquid crystals; nanoparticles; photosensitive materials