Presentation on theme: "Confining Liquid Crystals to Nanoporous Molecular Sieves by Ligia Frunza NIMP, Bucharest - Magurele Bucharest, January 27 2004 National Institute of Materials."— Presentation transcript:
Confining Liquid Crystals to Nanoporous Molecular Sieves by Ligia Frunza NIMP, Bucharest - Magurele Bucharest, January 27 2004 National Institute of Materials Physics Bucharest-Magurele Romania L. Frunza
Outline L. Frunza Introduction confining effects aim of the investigations Experimental materials (molecular sieves & confining organics) methods of investigation Results : dielectric spectroscopy DSC, DTA, TG FTIR optical microscopy/CCV Co-operations: bilateral FP6 resources to collaborate
Introduction L. Frunza C onfining effects Source of confining effects: size restriction polydispersity connectivity confining topology + surface effects Changes of confined material: physical properties chemical properties
Introduction Aim of the investigations L. Frunza Molecular sieves N anoporous materials offering arrays of pores and cavities with known geometry Substitution in their framework may lead to a variety of guest- host interactions New structures are continuously synthesized Confined matter: liquid crystals different other organics Studies aimed to investigate influence of the confinement on phase transitions (LC behavior) thermal stabilization anchoring mode of the molecules at the surface of the molecular sieves location of the organic molecules in the loaded samples inside the pores and/or cavities on the outer surface of the grains / agglomerates Potential applications of composites based on molecular sieves microlasers, sensors, biology (by functionalization), catalysts…
Results Confinement of liquid crystals L. Frunza Empty molecular sieves L. Frunza, S. Frunza, A. Schönhals, et al., J. Non-cryst. Solids, 307-310 (2002) 503. L. Frunza, H. Kosslick, A. Schönhals, et al., Proceedings SPIE-4799 (2002) 230. L. Frunza, S. Frunza, A. Schönhals, et al., Stud. Surf. Sci. Catal. 142 (2002) 1323. L. Frunza, H. Kosslick, S. Frunza, et al J. Phys. Chem B. 106 (2002) 9191.
Results Confinement of liquid crystals L. Frunza Two relaxation processes may appear. The slow relaxation process is a new one, due to surface layer. Its temperature dependence follows a VFT law. 1 2 3 T = 360 K 1) Bulk 8CB 2) 8CB(A)/AlMCM-41 3) 8CB(B)/AlMCM-41 Loaded molecular sieves S.Frunza, A.Schönhals, L.Frunza, et al., Chem.Phys. Lett.307 (1999) 167. S. Frunza, L. Frunza, A. Schönhals, J. Phys. IV France, 10 (2000), Pr7-115. S. Frunza, L. Frunza, M. Tintaru, et al., Liq. Cryst. Accepted Jan. 2004
L. Frunza Results Thermal analysis DTA curves: several endothermal and exothermal processes (oxidation/decomposition) DTA curve do not have the same shape as the corresponding DTG curve thermal process involving surface species
L. Frunza Results DSC Partially filled samples with low filling degree do not show phase transitions Completely filled samples: A part of confined 8CB shows phase transitions Downward shift of te peak temperature C-S A phase transition has the biggest shift correlation between the depression of the crystallization temperature and the reciprocal diameter of the pores cannot be established Most of the confined 8CB does not show any phase transitions S. Frunza, L. Frunza, A. Schönhals, et al., Europhys. Lett. 56 (2001) 801. L. Frunza, S. Frunza, A. Schönhals, et al., Stud. Surf. Sci. Catal. 142 (2002) 1323. S. Frunza, H. Kosslick, A. Schönhals, et al., J. Noncryst. Solids 325 (2003) 103.
L. Frunza Results In situ FTIR spectroscopy 8CB/AlSBA-15 CN vibration is described as a vibration of a localized group Species: Bulk-like LC (2226 cm -1 ) Randomized state (ca. 2230 m -1 ) Hydrogen bonded (2241 cm 1 ) L. Frunza, S. Frunza, A. Schönhals, et al., J.Molec. Struct. 563-564, 491-495 (2001). L. Frunza, H. Kosslick, U. Bentrup, et al., J. Molec. Str. 651-653 (2003) 341-347. L. Frunza, S. Frunza, I. Enache, et al., Mol. Cryst. Liq. Cryst. Accepted September 2003.
L. Frunza Results Confinement of Jacobsen complex J/AlMCM-41 L. Frunza, H. Kosslick, H. Landmesser, et al., J.Mol.Catal.123, 179-187 (1997) L. Frunza, I. Enache, I. Nicolaie, et al., BPU-5, Serbia, August 2003. L. Frunza, I. Nicolaie, S. Frunza, et al., ICC, Paris, France, July 2004. Water amount drcreases by increasing temperature. Jacobsen complex anchoring to the surface is an activated process.
T. Beica, R. Moldovan, M.R. Puica, S. Frunza, Liq. Cryst. 29 (2002) 1275. T. Beica, R. Moldovan, Irina Zgura, et al., BPU5, August 25-29, 2003, Serbia T. Beica, R. Moldovan, M. Tintaru, et al., Liq. Cryst. Accepted Dec. 2003 Results Lyotropic liquid crystals Confinement is constructed during synthesis of nanopores Some results on studies concerning lyotropic micelles are given in a Poster of T. Beica, R. Moldovan, M. Tintaru I. Zgura, S. Frunza L. Frunza
Co-operations Bilateral scientific agreements: Germany, Berlin ACA Hendrik Kosslick Rolf Fricke Ursula Bentrup Irene Pitsch H.-L. Zubowa BAM Andreas Schoenhals COORDINATION ACTION CONCORDE - Co-ordination of Nanostructured Catalytic Oxides Research and Development in Europe Framework Programme FP6 Priority 3 Nanotechnology and nanosciences, knowledge-based multifunctional materials, new production processes and devices
L. Frunza Acknowledgements Team of Liquid Crystals and Surface Interactions (NIMP): Stefan Frunza Ligia Frunza Traian Beica Mihaela Tintaru Irina Zgura Irina Nicolaie Rodica Moldovan Organizers of the National Seminar of Nanoscience and Nanotechnology Bucharest 2004