title: Molecular relaxation and microscopic structure of multilayers and superlattices of a photosensitive liquid-crystalline polymer.
abstract: We report a detailed study of photoinduced changes in the microscopic structure of monolayers, multilayers, and superlattices of a photosensitive side chain liquid crystalline polymer, deposited by the Langmuir-Schaefer technique. We probe both out-of-plane and in-plane ordering and its changes due to optical pumping of the trans-cis photoisomerization transition of the azobenzene side chain in an azopolyacrylate. Microscopic structure was studied mainly by synchrotron radiation x-ray reflectometry and grazing incidence diffraction; we also used null-ellipsometry and atomic force microscopy. Our results provide a quantitative modeling of the structural changes and corresponding relaxation times taking place as a function of confinement, temperature and optical pumping, and in particular confirm previously reported ellipsometric results on such changes as a function of sample thickness. This allows a quantitative description of the effects of reduced dimensionality on the structural transitions in this glass-forming system.
authors.affiliation: Dipartimento di Fisica and INFM, Università di Parma, Parco Area delle Scienze 7/A, I-43100 Parma, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Cristofolini
authors.forename: M P
authors.initials: MP
authors.lastname: Fontana
authors.forename: T
authors.initials: T
authors.lastname: Berzina
authors.forename: O
authors.initials: O
authors.lastname: Konovalov