Structural studies of cubic phases

Structural studies of cubic phases Marianne Impéror-Clerc LPS -UMR 8502-, UPS, Orsay Ia3d Im3m Molecules, phases and self-assembly ŠWide range of ...
Author: Aubrey Wilkins
2 downloads 3 Views 3MB Size
Structural studies of cubic phases Marianne Impéror-Clerc LPS -UMR 8502-, UPS, Orsay

Ia3d

Im3m

Molecules, phases and self-assembly ŠWide range of molecular compounds ŠSelf-assembly ŠSupramolecular structures, periodic at the nanoscale ŠThe symmetry of these organised phases are the same for all molecular compounds Š Templating of nanostructured materials

Molecules and self-assembly organic chemistry compounds OH Cn H

NO 2

O O Cn H

O 2n+1 O

2n+1

OH

NO 2

two immiscible parts at the molecular level : - hydrophilic/hydrophobic - polar/apolar

metallomesogens, dendrimers

self-assembly

industrial compounds : surfactants, cosmetics, food, biochemistry O

supramolecular structures, periodic at the nanoscale

O-Na+

EOmPOnEOm CH3(CH2)10COO-Na+

biological molecules : fatty acids, lipids

tribloc copolymers

Sequence of mesophases balance between the two parts –hydrophilic/hydrophobic or polar/apolarphases directes

Micellaire 3D

hex 2D

phases inverses

intermédiaire 3D lamellaire

courbure

courbure positive

courbure nulle

courbure négative frac vol para

The mesophase morphology results from the global optimisation of the nanosegregation between the two immiscible parts

Micellar cubic phases ŠDifferent types of packing of micelles ŠNon-ionic CnEOm/water systems Šhcp packing Anne-Marie Levelut (LPS, Orsay) Jean-François Sadoc (LPS, Orsay) Xiangbing Zeng (Sheffield University, UK)

Types of observed packing of micelles hard sphere packing fcc

tetrahedral close packing –tcp-

hcp

Pm3n

120°

Z = 12

Fm3m

P63/mmc

Z = 14

hard-sphere potential

Fd3m

Z = 15

bcc

Z = 16 b

repulsive long-range potential

y z

x

P42/mnm c

Im3m

a

Packing of hard spheres How to stack oranges ???

hard sphere packing fcc and hcp

conjecture de Kepler, 1611: No packing of balls of the same radius in three dimensions has density greater than the face-centered cubic packing. T. C. Hales, A proof of the Kepler conjecture. 1998-2005 …. C

A

fcc and hcp : same compacity

B

B

fcc has a very slightly more high entropy than hcp

A

A

fcc

hcp

Packing of « soft » spheres ? area minimisation

tetrahedral close packing –tcpFranck, Kasper, 1958

micellar phases of surfactants J. Charvolin, J. F. Sadoc, 1988

soap foams

dendrimers

Soap film area minimisation

P. Ziherl, P., R. D. Kamien, 2001 maximizing entropy of the dendrimer corona chains by minimizing the contact area

Geometrical approach

D. Weaire, R. A. Phelan, 1994

Pm3n

Pm3n is an ideal periodic foam with equal cell volumes -Kelvin conjecture-

Non-ionic CnEOm micellar phases O

O

CH3(CH2)n-1 (OCH2CH2)mOH

O

O

OH

C12EO12

C12EO8

hcp

Pm3n Pm3n

M. Clerc J. Phys. II France (1996)

M. Imai J. Chem. Phys. (2005)

P. Sakya, J.M. Seddon Langmuir (1997)

hcp packing in C12E8

single-crystal analysis P63/mmc c/a=(8/3)1/2 c

A B A B A

M. Clerc J. Phys. II France (1996)

b

b

b a

c

a

a

c

120 100 80

FF : form factor core/shell model (110)

(a)

(102)

140

(100) (002)

Bragg peak intensities

(101)

hcp packing in C12E8

60

(103)

40 20 1

2

3

4

electron density around a micelle electron density reconstruction

X. Zeng, M. Impéror-Clerc, J. Phys. Chem B (2007)

Conclusion about micellar cubic phases

Š In project : electron density reconstructions for bcc and Pm3n Š link between the shape of the micelles and the type of packing : hard sphere packing or tcp

Thermotropic cubic phases ŠMany examples of Ia3d bicontinuous phases ŠA complex tri-continuous Im3m cubic phase : structure solving using the inverse method Anne-Marie Levelut, Michèle Veber (LPS, Orsay) Goran Ungar, Xiangbing Zeng (Sheffield University, UK)

Bicontinuous Ia3d cubic phase r l

ε

surface G

electron density reconstruction

V. Luzzati Nature (1967)

Gyroid bicontinuous cubic O. Terasaki and coll. JACS (2004)

Two cubic phases formed by the ANBC-n compounds NO 2 O

OH Cn H

O Cn H

O 2n+1 O

2n+1

ANBC-n

OH

NO 2

Im3m Structural model ?

M. Impéror-Clerc, M. Veber, A.M. Levelut ChemPhysChem (2001)

n : alkyl chain length S. Kutsumizu et al. Liquid Crystals. (2002)

10 % mixture : Ia3d-Im3m reversible phase transition NO 2 OH

pure ANBC-18

Cn H

O O Cn H

O 2n+1 O

2n+1

OH

NO 2

K

125°C

SmC

156°C

Ia3d

197°C

I O C 12H 25

mixture with 10 % 3,5-didodecyloxobenzoic acid K

120°C

SmC

125°C

Ia3d Ia3d

175°C 145°C

Im3m

200°C

O OH

I

Im3m

aIm3m = 17.3 nm

aIa3d = 11.7 nm dSmC = 4.6 nm d211 = 4.8 nm

O C 12H 25

size ratio 1.5

d321 = 4.6 nm

Im3m single-crystal data After slow cooling from the isotropic liquid phase … 258< α

Suggest Documents