Crystallisation of
“Simple” Molecules
Franck ARTZNER
[email protected]
1) Chirality influence on molecular packing ?
2) What does Control hexadecane crystallisation ?
3) Polymorphism of trilaurin (LLL)
Molecular Packing
of aliphatic chains
Parallel
+
=
=
Perpendicular
+
=
=
Can Chirality Control Packing ?
2-hexadecanol
2-heptadecanol
Triclinic
Parallel
Orthorhombic
perpendicular
Can Chirality Control Packing ?
CHIRAL (S)
(S)
RACEMIC (R+S)
(S)
(S)
(R)
C.Alonso , F.Artzner, B.Suchod, M.Berthault, O. Konovalov, J. Pecaut, D.Smilgies, A.Renault
J. Phys.Chem. B. 2001, 105 (51), 12778-12785.
Chirality Can Control Packing !
RACEMIC (R+S)
CHIRAL (S)
Hydrogen Bonds
(S)
(S)
(S)
(S)
(R)
(S)
(S)
(S)
(S)
Triclinic
Parallel
C2 two-fold axis
S!S
Orthorhombic
Perpendicular
g : glide MIRROR
R!S
Crystallisation of
“Simple” Molecules
1) Chirality influence on molecular packing ?
2) What does Control hexadecane crystallisation ?
3) Polymorphism of trilaurin (LLL)
Why hexadecane crystallise
at exactly 16.51°C ?
Slow cooling
Crystallisation in 2 steps !!
Crystal
Transient
phase ?
- Nucleation / growing
Liquid
- Homogenous Crystallisation
Science 1999, 283,529
Crystal
Transient
Liquid
Crystal and Rotator Phases of alkanes
Crystal
Triclinic
Parallel
Rotator Phase
Orthorhombic
perpendicular
Hexagonal
Ref: Doucet 80’s
Sirrota 90’s
Calorimetry of Tricosane
nC23H48
Rotator => Crystal
Supercooling
Kinetic nucleation
Solid
Rotator
Rotator
Microcalix
0.02°C/min
Liquid
Liquid
Liquid => Rotator
No supercooling
"Thermodynamical
equilibrium"
Hliquid > Hrotator > HCrystal
Sliquid > Srotator > SCrystal
Temperature (°C)
Crystal and Rotator Phases
Crystal
- Nucleation / Growing
- Supercooling
Rotator Phase
- Homogeneous crystallisation
- Crystallisation at equilibrium
Structure of rotator phases
by X-ray diffraction
nC23H48
C6
FT
6-fold axis
(4.2Å)-1
LURE / D43
4.2Å
6-fold axis
Alkane Rotator phases : translationnal disorder
ESRF/ID2/IP/750mm
nC23H48
LURE/D43/IP/75mm
+/- 1.27Å
discret
+/- 0.2Å
continuous
Stacking fault = oscillation
Sliding = localized
Crystal and Rotator Phases
Crystal
- Nucleation / Growing
- Supercooling
- Molecular Order
Rotator Phase
- Homogeneous crystallisation
- Crystallisation at equilibrium
- Molecular Disorder
Polymorphism of Alkane Rotator Phases
Low enthalpy transitions
Large polymorphism
nC23H48
Microcalix
0.02°C/min
Temp. (°C)
C
41
39
RV
43
tilt
RI
46
RII
48
L
distorsion
distorsion
tilt
RII
RI
RIV
RV
LURE / D22
Small Angle X-ray Scattering
nC23H48
31.5Å
Wide Angle X-ray Scattering
4.22Å
31.1Å
3.83Å
40°C
RV
TILT
RI
RII
49°C
4.12Å
Crystal and Rotator Phases
Crystal
- Nucleation / Growing
- Supercooling
- Molecular Order
Rotator Phase
- Homogeneous crystallisation
- Crystallisation at equilibrium
- Molecular Disorder
Intermediate properties
between liquid and crystal
Why hexadecane crystallise at 16.51°C ?
Gibbs Free Energy : G
G
supercooling
Rotator
Crystal
Liquid
16.51
C
18.51
T
L
R
Why hexadecane crystallise at 16.51°C ?
Gibbs Free Energy : G
G
supercooling
Rotator
Crystal
Liquid
16.51
C
18.51
T
L
R
Why hexadecane crystallise at 16.51°C ?
Gibbs Free Energy : G
G
No supercooling
Rotator
Crystal
Liquid
16.51
18.51
T
L
C
R
Crystallisation in rotator phase
at 16.51°C
Why hexadecane crystallise at 16.51°C ?
Gibbs Free Energy : G
G
Crystal nucleation
Rotator
Crystal
Liquid
16.51
C
18.51
T
L
R
Fast Crystallisation
at 16.51°C
Crystallisation of
“Simple” Molecules
1) Chirality influence on molecular packing ?
2) What does Control hexadecane crystallisation ?
3) Polymorphism of trilaurin (LLL)
C. Allais Ph.D. thesis
Trilaurin (LLL) polymorphism
X-ray
LURE / D43
Calorimetry
β1
10°C/min
β2
β1’
β2’
α
[L]
16°C
β’
[L]
28°C
β1
[L]
32°C
β2
α
45°C
L
q[Å-1]
C. Allais Ph.D. thesis
Trilaurin (LLL)
Control of polymorphism
Gibbs Diagram
G
α
One stable phase
L
$
"
!
β’
%
"
β2
!
!
β1 #
"
0
!
20
40
0°C
T(°C)
50°C
β2
45°C
L
Triglycerides vs alkanes
Hexagonal phase
LURE / D43
Alkane in
Rotator RII
LLL in α
q[Å-1]
Disorder identical !!!
Triglycerides vs alkanes
Orthorhombic phase
nC23H48
LURE / D43
Trilaurin
Chain
β’
Packing ?
sub α
Or ?
Rotator RV
q[Å-1]
β’ Believed to be an orthorhombic perpendicular subcell
(Handbook of Lipid Research, Donald Small, p348)
Conclusions ?
1) Sensibility molecular packing of crystal (chirality,…)
2) Rotator phases are intermediates of crystallisation
3) Alkane rotator phases analog to
disordered phases of TG, α (and β’..?)
ROTATOR PHASES (open questions) :
- Molecular Packing (order and disorder)
- Rotator => Crystal Transition
- ….
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Many thanks to
Chatenay Malabry group
- Cécile Allais (Ph.D. student)
- G. Keller (Microcalix)
- M. Ollivon
Chirality
- C. Alonso
- A. Renault (Rennes)
LURE Synchrotron
- D. Durand (D43)
- P. Lesieur (D22)
ESRF Synchrotron
- T. Narayanan (ID2)