Transcript Kein Folientitel
National Institute of Materials Physics Bucharest-Magurele Romania
Confining Liquid Crystals to Nanoporous Molecular Sieves
by
Ligia Frunza
NIMP, Bucharest - Magurele
Bucharest, January 27 2004
L. Frunza
Outline
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Introduction confining effects aim of the investigations
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Experimental materials (molecular sieves & confining organics) methods of investigation
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Results : dielectric spectroscopy DSC, DTA, TG FTIR optical microscopy/CCV
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Co-operations: bilateral FP6 resources to collaborate
L. Frunza
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Introduction
Source of confining effects:
C onfining effects
Changes of confined material:
size restriction polydispersity connectivity confining topology + surface effects physical properties chemical properties
L. Frunza
•
Introduction Aim of the investigations
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
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Confined matter: New structures are continuously synthesized liquid crystals different other organics
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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
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Potential applications of composites based on molecular sieves microlasers, sensors, biology (by functionalization), catalysts…
L. Frunza
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Experimental Molecular sieves. AlMCM-41, AlSBA-15, SiNMS-F Synthesis: NIMP(INCDFM) partners
L. Frunza
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Experimental Confined matter
CH 2 CH 2 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 O Na + L. Frunza
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Experimental Investigation methods
IR & UV-vis spectroscopy in situ
Broadband dielectric spectroscopy (partners)
Thermal analysis (partners) differential thermal analysis (DTA) differential scanning calorimetry (DSC) Optical microscopy /CCV camera Luminescence / thermoluminescence Others thermogravimetry (partners) X-ray diffraction electron microscopy nitrogen absorption meas. (partners)
L. Frunza
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Results Confinement of liquid crystals Bulk 8CB
I I S A log ( f [ Hz]) 333 60 313 40 T ( T ° C ) [K] A.Schoenhals, H.-L.Zubowa, R.Fricke,
S.Frunza, L.Frunza, R.Moldovan,
Cryst. Res. Technol.
34
, 1309 (1999) L. Frunza
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Results
-1 -2 -3 0 2 log (f[Hz )) 4
Confinement of liquid crystals
Empty molecular sieves
6 320 300 280 260 240 220 (B) T [K] SiNMS-F 2 -1 -2 1 0 -3 3.0
3.5
AlSBA-15 NMS-F 4.0
1000/(T[K]) 4.5
5.0
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.
L. Frunza
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Results
1) Bulk 8CB 2) 8CB(A)/AlMCM-41 3) 8CB(B)/AlMCM-41
Confinement of liquid crystals Loaded molecular sieves
1 •
Two relaxation processes may appear.
3 2 •
The slow relaxation process is a new one, due to surface layer. Its temperature dependence follows a VFT law.
T = 360 K
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
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Results Thermal analysis
(A) (B) 400 600 8CB/AlSBA-15 8CB/SiSBA-F 8CB bulk 800 Temperature/ K 1000 400 600 800 Temperature/ K 1000 •
DTA curves: several endothermal and exothermal processes (oxidation/decomposition)
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DTA curve do not have the same shape as the corresponding DTG curve thermal process involving surface species
L. Frunza
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Results
280 295 300 305 8CB bulk 8CB/SiSBA-F 8CB/AlSBA-15 300 Temperature /K 320 340
DSC
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Partially filled samples with low filling degree do not show phase transitions
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Completely filled samples:
A part of confined 8CB shows phase transitions
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Downward shift of te peak temperature
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C-S A phase transition has the biggest shift
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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
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Results In situ FTIR
spectroscopy
2200 2225 2250 (A) 623 K 598 K 573 K 548 K 523 K 498 K 473 K 448 K 423 K 398 K 373 K 323 K 298 K
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 )
2200 2225 2250 Wavenumbers /cm -1
8CB/AlSBA-15 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
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Results
0 2 4
J/AlMCM-41 T
Confinement of Jacobsen complex
0.75
J/AlMCM-41
0.50
1605 cm -1 1643 cm -1 1873 cm -1 1995 cm -1 0.25
0 100 200 300 Temperature / o C 400 500 1500 2000 2500 3000 Wavenumbers (cm -1 ) 3500 4000
Water amount drcreases by increasing temperature.
Jacobsen complex anchoring to the surface is an activated process.
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.
L. Frunza
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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 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 L. Frunza
Bilateral scientific agreements:
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Co-operations
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
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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
L. Frunza