how do hydrogen bonds influence thermophoresis? · hydrogen bonds: temperature effect [kishikawa,...
TRANSCRIPT
21. September 2016
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How do hydrogen bonds influence thermophoresis?
| Simone Wiegand,
Doreen Niether, Jan K.G. Dhont
21/09/16 Folie 2
Thermophoresis – the effect
(…, thermodiffusion, Soret effect)
No microscopic understanding
21/09/16 Folie 3
Thermophoresis – the effect
3
D - diffusion coefficient, w - concentration,DT - thermodiffusion coeff.,
Steady state
– flux,T – temperature,ST Soret coefficient
21/09/16 Folie 4
Mass effect: animationcold molecules hot molecules
cold side hot side
“kinetic gas model”higher momentum transfer from the warm side
Enrichment of the heavy particles on the cold side
21/09/16 Folie 5
Thermophoresis: Where is it used?
Application examples: “Characterization of Soft Matter”Thermal field flow fractionation
SW., Introduction to thermal gradient related effects, in Functional Soft Matter, J.K.G. Dhont, et al., Editors. 2015, Forschungszentrum Jülich: Jülich. p. F4.1-F4.24.
21/09/16 Folie 6
Thermophoresis: Where is it used?
Mic
rosc
ale
Ther
mop
hore
sis:
Te
chno
logy
and
App
licat
ions
//Nan
oTem
perG
MB
H
Application examples: “Biochemical reactions”Microscale thermophoresis
21/09/16 Folie 7
Hydrogen bonds: temperature effect
At low temperatures: minimization of the free energy
F = U – TSby forming hydrogen bonds (ΔU<0).
water goes to the cold side
At high temperatures: minimization of the free energy
F = U – TS by entropy production (ΔS>0).
water goes to the warm side
[Wang, Z., H. Kriegs, and SW J. Phys. Chem. B, 116 (2012) 7463.]
Assuming local thermodynamic equilibrium
21/09/16 Folie 8
Hydrogen bonds: temperature effect
[Kishikawa, Y., SW, and R. Kita, Biomacromolecules, 11 (2010) 740]
Many, but not all aqueoussystems show a similartemperature dependence
[Iacopini et al., Eur. Phys. J. E, 19(2006) 59]
0 10 20 30 40 50 60-0.1
0.0
0.1
0.2
PEO/we
lysozyme
DNA
DNA
(a)
14
PEO/water
DNA
-lactoglobine
6
dextran
dextrandextran
pullulan
temperature / °C
ST /
K-1
ST < 0
ST > 0
21/09/16 Folie 9
Validity of the empirical formula?
T
0T 1 expS T TST
T
A. Königer, et al., Philos. Mag., 89 (2009) 907.
ethanol/water
10 20 30 40
-5
0
5
10
0.051 0.100 0.152 0.1983 0.2512 0.3016 0.3538 0.3987 0.4998 0.5921
ST /
10-3K-1
temperature /°C
w =
[O. Gereben, Journal of Molecular Liquids, 211 (2015) 812-820]
• “pure water rings are formed”• clumping of like molecules
20 mol % ethanol
Breaks down at low concentrations when the homogeneity of the mixture at the molecular level is an issue.
waterrich
ethanolrich
21/09/16 Folie 10
Systematic study of amides
Urea Formamide Acetamide N-Methyl-formamide
N,N-Dimethyl-formamide
More hydrophilic
22 2 2
Why amides? “.. serve as model of the peptide bond “ [Y. Lei et al. JPC A, 107 (2003) 1574]
21/09/16 Folie 11
Temperature dependence
• at low concentrations (w 0.3):
• more flexible fit function neededto describe T-dependence athigher concentrations:
urea in water22
T
0T 1 expS T TST
T
TT expS T a bS T
[Story and Turner, Faraday Trans., 65 (1969) 1810]
20 40 600
1
2
3
w=0.5 w=0.4 w=0.3 w=0.2 w=0.1 w=0.05 w=0.02
ST /
10-3K
-1
temperature /°C
w=0.226 w=0.154 w=0.092 w=0.025
21/09/16 Folie 12
Temperature dependence
• at low concentrations (w < 0.2):
• more flexible fit function neededto describe T-dependence athigher concentrations:
0 20 40 600
1
2
3 conc. (w.f.) 0.2
0.02 0.3 0.05 0.5 0.1 0.7
ST /
10-3K
-1
temperature /°C
formamide in water
T
0T 1 expS T TST
T
2
TT expS T a bS T
[Niether, Afanasenkau, Dhont, SW, PNAS, 113(2016) 4272]
21/09/16 Folie 13
0 20 40 600
1
2
3
conc. (w.f.) 0.2
0.02 0.3 0.05 0.5 0.1 0.7
ST /
10-3K-1
temperature /°C
Structural explanationMolecular dynamic simulations[Elola & Ladanyi, JCP 125,(2006) 184506]
suggest the following picture:
conc. = ?
slope ST > 0 slope ST < 0
low w
only FA-Whydrogen bonds
higher w
also FA-FAhydrogen bonds
21/09/16 Folie 14
POSTER – P02-057
A way to achieve sufficiently high formamideconcentrations to form prebiotic nucleobases under early earth conditions
by
Doreen Niether
21/09/16 Folie 15
„log P“ a „Scale bar“ for hydrogen bonding strength?
octanolunionizedwater
[ ]log log( )[ ]
solutePsolute
Hydrophilic compound: log P < 0octanol
water
octanolwater
Hydrophobic compound: log P > 0
Marvin 16.5.2.0, 2016, ChemAxon (http://www.chemaxon.com)G. Klopman et al. J Chem Inf Comp Sci, 34 (1994) 752-781.V. N. Viswanadhan et al. J Chem Inf Comp Sci, 29 (1989) 163-172.
urea
21/09/16 Folie 16
„log P“ a „Scale bar“ for hydrogen bonding strength?
-1.30 -1.13 -1.03 -0.89 -0.64
More hydrophilic
22 2 2
Marvin 16.5.2.0, 2016, ChemAxon (http://www.chemaxon.com)
Urea Formamide Acetamide N-Methyl-formamide
N,N-Dimethyl-formamide
Log P =
21/09/16 Folie 17
„log P“ a „Scale bar“ for polar solvents ?
-10 -5 0 5-1.5
-1.0
-0.5
0.0
log
P
slope ST(T) / 10-5K-210 20 30 40 50 60 700
2
4
6
8
Ethanol (Königer) Dimethylformamide Acetamide Methylformamide Urea Formamide
ST /
K-1
T / °C
5wt% in water
O
NH2Temperaturedependence of STis correlated withlog P
[Königer, A
., et al., Philos. M
ag., 89(2009) 907]
Low concentration
21/09/16 Folie 18
Comparison: low and high concentration
urea
formamide
acetamide
NMF
DMF
0 2 4 6ST (50wt% ) ST ( 5wt% ) / 10-3K-1
@ 10°C
hydrophilic systems:increasing concentration:solute becomes more thermophobic
hydrophobic systems:increasing concentration:solute becomes more thermophilic
21/09/16 Folie 19
„log p“ scales ST change with concentration
-1.5 -1.0 -0.5 0.0 0.5-1.5
-1.0
-0.5
0.0
log
P
ST(50wt%-5wt%) /10-2K-1
O
NH2
21/09/16 Folie 20
„log p“ scales ST inrespect to c and T
correlation between log P and the change of ST with… concentration… temperature
-10 -5 0 5-1.5
-1.0
-0.5
0.0
log
Pslope ST(T) / 10-5K-2
-1.5 -1.0 -0.5 0.0 0.5-1.5
-1.0
-0.5
0.0
log
P
ST(50wt%-5wt%) /10-2K-1
O
NH2
21/09/16 Folie 21
Take home message
T
0T 1 expS T TST
T breaks down at low wdue to inhomogeneities
Log P correlates with temperature dependence of ST
Log P correlates with concentration change of ST
breaks down at high w
Thermophoresis issensitive to changes of the hydration layer
21/09/16 Folie 22
Thanks to many people and …
… thank you for your attention
FZ Jülich Jan Dhont‘s group(ICS-3)
Rio Kita‘s labKazuya EguchiTokai University, Japan
Fernando Bresme‘s groupSilvia di LecceImperial College London, GB
21/09/16 Folie 23
21/09/16 Folie 24
How do we measure?
IR-TDFRS – InfraRed -Thermal Diffusion Forced Rayleigh Scattering
Measured quantity:Intensity of the diffracted beam
[SW
et al., J. Phys. C
hem. B
, 111(2007) 14169]
Advantages:• small T • no fluorescent labeling
required• wide molecular range Disadvantages:• buffer solutions: difficult• colloids >100 nm: difficult.
Typical gradients: 1K/m
21/09/16 Folie 25
Formamide vs. N-methylformamide
O
NH2
[A. K. H. Weiss, et al. PCCP, 13 (2011) 12173]
“Whereas formamide is almost encaged by the oxygen density, the influence of the methyl group disrupts this pattern rigorously”
21/09/16 Folie 26
Dimethylformamide/water
[Lei, Y., et al., JPC A, 107(2003) 1574Vasudevan, V. and S.H. Mushrif, J. Mol. Liq., 206(2015) 338 ]
“The increases in the peaks of RDFs between water molecules are not so much caused by an increase in the structure of water as they are by the tendency of water to remain in aggregates in the mixtures.”
doubts about the Force field ?
21/09/16 Folie 27
20 40 60-10123456 Dimethylformamide
5 wt% 50 wt%
Methylformamide 5 wt% 50 wt%
Acetamide 5 wt% 50 wt%
Formamide 5 wt% 50 wt%
Urea 5 wt% 50 wt%
ST /
10-3
K-1
T / °C
Comparison: low and high concentration
21/09/16 Folie 28
Principle Microscale thermophoresisS
W., Introduction to therm
al gradient related effects, in Functional Soft M
atter, J.K.G
. D
hont, et al., Editors. 2015, Forschungszentrum
Jülich: Jülich. p. F4.1-F4.24.