Confining Liquid Crystals to Nanoporous Molecular Sieves

by

Ligia Frunza

NIMP, Bucharest - Magurele

Bucharest, January 27 2004

National Institute of Materials PhysicsBucharest-Magurele

Romania

L. Frunza

Outline

L. Frunza

•Introductionconfining effects aim of the investigations

•Experimentalmaterials (molecular sieves & confining organics)methods of investigation

•Results : dielectric spectroscopyDSC, DTA, TGFTIRoptical microscopy/CCV

•Co-operations: bilateral FP6

resources to collaborate

•Introduction

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Confining effects

Source of confining effects:

size restrictionpolydispersityconnectivity confining topology

+surface effects

Changes of confined material:

physical properties

chemical properties

•IntroductionAim of the investigations

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Molecular sieves Nanoporous 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 investigateinfluence of the confinement on

phase transitions (LC behavior)thermal stabilization

anchoring mode of the molecules at the surface of the molecular sieveslocation of the organic molecules in the loaded samples

inside the pores and/or cavitieson the outer surface of the grains / agglomerates

•Potential applications of composites based on molecular sievesmicrolasers, sensors, biology (by functionalization), catalysts…

•ExperimentalMolecular sieves. AlMCM-41, AlSBA-15, SiNMS-F

L. Frunza

Synthesis: NIMP(INCDFM)partners

AlSBA-158.5 nm size

AlMCM-412 nm size

hexagonal structure

AlSBA-158.5 nm size

AlMCM-412 nm size

hexagonal structure

SiNMS-F17.2 nm size

cellular structure

SiNMS-F17.2 nm size

cellular structure

•ExperimentalConfined matter

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Thermotropic Liquid Crystals

8CB4-n-octyl-4'-cyano-biphenyl

C - SA = 295 K / S - N = 306.5 K N - I = 313.5 K

Thermotropic Liquid Crystals

8CB4-n-octyl-4'-cyano-biphenyl

C - SA = 295 K / S - N = 306.5 K N - I = 313.5 K

L y o t r o p i c L i q u i d C r y s t a l s

S D S( S o d i u m d o d e c y l s u l p h a t e )

S D S / w a t e r / d e c a n o ln e m a t i c c a l a m i t i c

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 3

O S O - Na +

O

O

Hydrophilic headHydrophobic chain

L y o t r o p i c L i q u i d C r y s t a l s

S D S( S o d i u m d o d e c y l s u l p h a t e )

S D S / w a t e r / d e c a n o ln e m a t i c c a l a m i t i c

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 2

CH 3

O S O - Na +

O

O

Hydrophilic headHydrophobic chain

Organic complexes

Jacobsen complex

enantioselective catalyst homogeneous catalysisheterogenization

Organic complexes

Jacobsen complex

enantioselective catalyst homogeneous catalysisheterogenization

•ExperimentalInvestigation methods

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IR & UV-vis spectroscopy in situBroadband 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 diffractionelectron microscopynitrogen absorption meas. (partners)

•Results Confinement of liquid crystals

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6.57.0

7.58.0

8.520

40

6080

-1.5

-1.0

-0.5

0.0

0.5

log

''

293

313

333

3D plot of dielectric loss

6.57.0

7.58.0

8.520

40

6080

-1.5

-1.0

-0.5

0.0

0.5

log

''

293

313

333

3D plot of dielectric loss

2 .6 2 .8 3 .0 3 .2 3 .4 3 .6

6

7

8

9

CSA

NI

log

(f p

[H

z])

1 0 0 0 K / T

R elaxa tio n ra tes vs . 1 /T

2 .6 2 .8 3 .0 3 .2 3 .4 3 .6

6

7

8

9

CSA

NI

log

(f p

[H

z])

1 0 0 0 K / T

R elaxa tio n ra tes vs . 1 /T

Bulk 8CB

A.Schoenhals, H.-L.Zubowa, R.Fricke, S.Frunza, L.Frunza, R.Moldovan, Cryst. Res. Technol. 34, 1309 (1999)

•ResultsConfinement of liquid crystals

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Empty molecular sieves

02

46

220240

260280

300320

-3

-2

-1

SiNMS-F(B)

log ''

T [K

]log (f[Hz))

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.

3.0 3.5 4.0 4.5 5.0

-3

-2

-1

0

1

2

AlSBA-15 NMS-F

log([s

])

1000/(T[K])

•Results Confinement of liquid crystals

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•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 K1) Bulk 8CB2) 8CB(A)/AlMCM-413) 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

400 600 800 1000

(B)

Wei

gth

loss

deriv

ativ

e

Temperature/ K

•DTA curves: several endothermal and exothermal processes (oxidation/decomposition)

•DTA curve do not have the same shape as the corresponding DTG curvethermal process involving surface species

400 600 800 1000

(A)

8CB/AlSBA-15 8CB/SiSBA-F 8CB bulk

He

at

flow

, a

.u.

Temperature/ K

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•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-SA 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

280 300 320 340

8CB bulk 8CB/SiSBA-F 8CB/AlSBA-15

Spe

cific

hea

t cap

acity

/JK

-1kg

-1

Temperature /K

295 300 305

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.

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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

Wavenumbers /cm-1

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.

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•Results Confinement of Jacobsen complex

1500 2000 2500 3000 3500 4000

4

2

0

T

Tra

nsm

issi

on

Wavenumbers (cm -1)

J/AlMCM-41

0 100 200 300 400 500

0.25

0.50

0.75

Abs

orba

nce

Temperature /oC

1605 cm -1

1643 cm -1

1873 cm -1

1995 cm -1

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, SerbiaT. 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

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L. Frunza

•Co-operationsBilateral scientific agreements:

Germany, Berlin ACAHendrik Kosslick Rolf FrickeUrsula Bentrup Irene PitschH.-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

•AcknowledgementsTeam of Liquid Crystals and Surface Interactions (NIMP):

Stefan FrunzaLigia FrunzaTraian BeicaMihaela TintaruIrina Zgura Irina NicolaieRodica Moldovan

Organizers of the National Seminar of Nanoscience and Nanotechnology Bucharest 2004