Molecular relaxation and microscopic structure of multilayers and superlattices of a photosensitive liquid-crystalline polymer.
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.
Cristofolini
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L
Dipartimento di Fisica and INFM, Università di Parma, Parco Area delle Scienze 7/A, I-43100 Parma, Italy.
Fontana
M P
MP
Berzina
T
T
Konovalov
O
O