Structure and Dynamics of Glycerol in Gamma-Alumina Nano-pores
G. Campos-Villalobos
…or why glycerol can move faster under confinement? G. Campos-Villalobos
The Classical Picture of Confined Liquids
The equilibrium and transport properties of liquids geometrically confined in nano-sized pores are dramatically different to those in the bulk state
Low mobility
1
Phase Transitions
L
The Curious Case of Glycerol
Temperature
Volume Liquid
Crystal
Glass (1)
Glass (2)
TmTg(1)Tg(2)
Glycerol is a glass-former
Cometics Bio-Inks Heterogeneous Catalysis
2
The Curious Case of Glycerol
3
The Curious Case of Glycerol
3
The Curious Case of Glycerol
3
The Curious Case of Glycerol
3
Model Systems
⇢conf =Mglycerol
Vpore
A measure of the pore saturation
Pore size
Glycerol in Gamma-Alumina
4
{100} hydroxylated facet exposed to the liquid. CLAYFF force-field
Gamma-Alumina
GlycerolOPLS-AA
T = 300K
Order and Symmetry Breaking at Interfaces
(a) (b) (c)Reduction of Pore Saturation
Fully saturated pore Bubble Adsorbed liquid films
⇢conf
5
(a)(b)
(c)
Order and Symmetry Breaking at Interfaces
-30 -20 -10 0 10 20 300
1
2
3
ρconf = 1.2ρconf = 1.0
-30 -20 -10 0 10 20 30-2
0
2
4
ρconf = 0.8ρconf = 0.6
-20 -10 0 10 200
1
2
3
ρ(z
) / ρ
bulk
ρconf = 0.4
-20 -10 0 10 20-2
0
2
4
W(z
) / k
BT
-10 -5 0 5 10
z / Å
0
1
2
3
-10 -5 0 5 10
z / Å
-2
0
2
4
lz = 60 Å
lz = 40 Å
lz = 20 Å
Fully saturated pore
Bubble
Adsorbed liquid films
Formation of discrete molecular layers close to the surface
6
Order and Symmetry Breaking at Interfaces
In-plane ordering
7
Interfacial Effects
The number of HB per molecule is spatially-dependent
8
Interfacial Effects
0.4 0.6 0.8 1 1.2
ρconf / g cm-3
0.6
0.7
0.8
0.9
1
n* H
B/O
H
lz = 60 Å
lz = 40 Å
lz = 20 Å
(a)(b)
(c)
Fully saturated pore
Bubble
Adsorbed liquid films
HB change with confinement length and density
9
Consequences on the Dynamics: HB Networks
0.4 0.6 0.8 1 1.2
ρconf / g cm-3
0
1
2
3
4
τ* H
B
lz = 60 Å
lz = 40 Å
lz = 20 Å
t = 0
r < rHB
r > rHB
HB lifetime
t = ⌧HB
10
Consequences on the Dynamics: Diffusion
-30 -20 -10 0 10 20 300369
ρconf = 1.2ρconf = 1.0
-20 -10 0 10 200246
D||(z
) / D
bulk
ρconf = 0.8ρconf = 0.6
-10 -5 0 5 10z / Å
0
1
2
3
ρconf = 0.4
lz = 60 Å
lz = 40 Å
lz = 20 Å
(a)(b)
(c)
Fully saturated pore
Bubble
Adsorbed liquid films
Local diffusion coefficient
11
Consequences on the Dynamics: Diffusion
-30 -20 -10 0 10 20 300369
ρconf = 1.2ρconf = 1.0
-20 -10 0 10 200246
D||(z
) / D
bulk
ρconf = 0.8ρconf = 0.6
-10 -5 0 5 10z / Å
0
1
2
3
ρconf = 0.4
lz = 60 Å
lz = 40 Å
lz = 20 Å
Local diffusion coefficient
12
Dconf =⌦Dk (z)
↵=
RlzDk (z) ⇢ (z) dzRlz⇢ (z) dz
Consequences on the Dynamics: Diffusion
0.4 0.6 0.8 1 1.2
ρconf / g cm-3
0
1
2
3
4
5
D*
lz = 60 Å
lz = 40 Å
lz = 20 Å
Global diffusion coefficient
Enhanced molecular self-diffusion in confinement
13
Outlook
1 2 3
The solid imposes a heterogeneity in the liquid, causing the structural and
dynamical properties to acquire a spatial dependence
The formation of interfaces with the solid and vacuum regions is found profoundly
affect the kinetics of breaking and re-formation of hydrogen
bonds
A necessary condition for the enhancement in the molecular diffusion is the partial saturation
of the pores
Acknowledgements
Alessandro Patti
Flor R. Siperstein
Carmine D'Agostino
THANK YOU!