Obiettivo Liquid crystal (LC) alignment on solid surfaces is a crucial topic for both fundamental research and LC applications, e.g. display devices. Most industrial applications are based upon LC alignment by rubbed polymers, giving a strong anchoring with planar or slightly tilted LC orientation. However, last decade industrial needs and progress in the study of surface LC phenomena impose the development of more sophisticated aligning technologies. Materials with wide range of anchoring energies, complex spatial distribution of easy orientation axis, bistable anchoring, are strongly required now for display technology, optical processing and storage, non-linear optics devices, and so on. In particular, several new LC devices have been proposed recently, needing weak zenithal anchoring and/or weak or degenerated azimuthal anchoring.A promising way to obtain weak, well-controlled and reproducible LC anchorings is the photoalignment of polymers by polarized UV light. Both zenithal and azimuthal anchoring strengths can be modified in this way, enabling the realisation of new, surface controlled devices, with superior optical quality, low driving voltages and potential bistability. However, as other weak anchorings, these alignment layers are sensitive to surface memory effects. This effect is caused by an anisotropic adsorption of molecules on the aligning surface and is observed for most aligning materials. The adsorbed oriented layer behaves as a new, anisotropic substrate and the weak anchoring slowly grows stronger, especially the azimuthal one. Moreover, a strong azimuthal torque applied on the surface rotates slowly the direction of the easy axis itself and the new direction remains after suppression of the torque. This slow easy axis gliding is related to the adsorption-desorption dynamics of the adsorbed layer.The main objective of the present project is to realize weak LC anchorings, free of anchoring memory effects, by developing new photoalignment polymers and processes for their deposition and orientation. The synthesis of the new polymers will be guided by preliminary experimental studies of the anchoring strength, memory and gliding on known photosensitive polymers and by development of theoretical models relating these properties to the polymer molecular structure and macroscopic organisation. The new materials will be fully characterized as aligning layers for commercial LC mixtures and will be applied in specific weak anchoring devices, recently proposed by the partners in the project, or to be developed during the project on the basis of the acquired new understanding of the liquid crystal surface physics. These devices, e.g. In-Plane-Sliding (IPSL) and Degenerated-Cholesteric-Anchoring (DCA) cells, are expected to give superior optical properties and low driving voltages.To solve the problem of a weak anchoring one needs detailed theoretical and experimental studies of the anchoring strength, the nature of the anchoring memory effect, the processes of adsorption and desorption of LC molecules on polymer surfaces, and syntheses of new materials. These problems will be solved by the consolidation of the efforts of the partners' teams, experienced in different fields of LC and polymer science: theoretical and experimental surface physics of LCs, physics and chemistry of polymer surface, electro-optics and optics of LCs, design and optimisation of LC devices. The innovative and complementary experience of the project partners will enable the development of a new direction of fundamental and applied liquid crystal studies - physics of weakly anchored memory-free liquid crystals - and the demonstration of principally new LC devices, based on memory-free photoaligning polymers with weak or zero anchoring strength. Programma(i) IC-INTAS - International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993- Argomento(i) 1B - Condensed Matter, Optics and Plasma Physics OPEN - OPEN Call Invito a presentare proposte Data not available Meccanismo di finanziamento Data not available Coordinatore NEMOPTIC Contributo UE Nessun dato Indirizzo Parc du Merantais, 1 rue Guynemer 78114 Magny les Hameaux Francia Mostra sulla mappa Costo totale Nessun dato Partecipanti (5) Classifica in ordine alfabetico Classifica per Contributo UE Espandi tutto Riduci tutto Institute of Bioorganic Chemistry and Petrochemistry Ucraina Contributo UE Nessun dato Indirizzo Murmanska street, 1 253660 Kiev Mostra sulla mappa Costo totale Nessun dato Kiev National Shevchenko University Ucraina Contributo UE Nessun dato Indirizzo Prospect Glushkova, 6 252022 Kiev Mostra sulla mappa Costo totale Nessun dato National Academy of Sciences of Ukraine Ucraina Contributo UE Nessun dato Indirizzo Prospekt Nauki 46 03028 Kiev Mostra sulla mappa Costo totale Nessun dato Universita degli Studi di Pisa Italia Contributo UE Nessun dato Indirizzo via Buonarroti 2 56100 Pisa Mostra sulla mappa Costo totale Nessun dato University of Montpellier II Francia Contributo UE Nessun dato Indirizzo Place Eugène Bataillon 34095 Montpellier Mostra sulla mappa Costo totale Nessun dato
