Molecular simulation of transport in liquids and polymers [Elektronische Ressource] / vorgelegt von Eduard Rossinsky

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• Publié par: technischen_universitat_darmstadt
• Publié le: 01 janvier 2010
• Nombre de lectures: 13
• Langue: English

Extrait

Molecular Simulation of Transport in Liquids
and Polymers




Vom Fachbereich Chemie
der Technischen Universität Darmstadt







zur Erlangung des akademischen Grades
eines Doktor rerum naturalium (Dr. rer. nat.)



genehmigte
Dissertation

vorgelegt von

Eduard Rossinsky, M.Sc. of Chemical Engineering

Aus Belgorod, Russian Federation



Berichterstatter: Prof. Dr. Florian
Müller-Plathe
Mitberichterstatter: Dr. Rolf Schäfer
Eingereicht am: 01.12.2009
Mündliche Prüfung am: 18.01.2010



Darmstadt 2010
D17 Acknowledgements
First of all, I would like to gratefully acknowledge the enthusiastic supervision of
Prof. Dr. Florian Müller-Plathe during this work. I am very grateful to him for giving me
the opportunity to work in his group. I will always be thankful for his wisdom,
knowledge, and deep concern. He has always been supportive and has given me the
freedom to pursue various projects without objection. He has also provided many
relevant and insightful discussions during this research. It has been a real honour to work
with him.
I would like to thank all my colleagues for creating a warm working-atmosphere.
Particularly, I would like to say a special thank-you to Konstantin B. Tarmyshov for his
help in facilitating my adjustment to the life in Darmstadt, and for his scientific support. I
am grateful to Michael C. Börn and Pavel Polyakov for their helpful discussions and for
their help during the final stages of this thesis. A special thanks to Gabriele General for
her positive outlook and her ability to smile in spite of any difficulties.
I would like to convey my heartfelt thanks to my home university, the Technion,
which helped me to achieve this high level of education. And of course, in the end, I
would like to mention, with special thanks, the support I received from my family and my
friends in Germany and Israel.
ITable of Contents

Acknowledgements………………………….…………………………………………….I
List of Figures………………………………..…………………………………………..IV
List of Tables…................................................................................................................VII
Abstract….......................................................................................................................VIII
Zusammenfassung.............................................................................................................XI
1. Introduction……………………………………..………………………………………1
References…………………………………………………………………………4
2. Theory and Method………………………….….………………………………………5
2.1 Thermal conductivity………………………………………………………….5
2.2. Soret effect……………………………………………………………………5
2.2.1 Theory and calculation………………………………………………5
2.2.2 Thermal Diffusion Forced Rayleigh Scattering……………………..6
2.3 Equilibrium molecular dynamics……………………………………………...9
2.4. Reverse non equilibrium molecular dynamics (RNEMD)…………………..11
2.5 References……………………………………………………………………13
3. Anisotropy of the thermal conductivity in a crystalline polymer: Reverse non-
equilibrium molecular dynamics simulation of the δ phase of syndiotactic polystyrene..14
3.1. Introduction………………………………………………………………….14
3.2. Methods……………………………………………………………………...16
3.3. Computational Details………………………………………………………17
3.4. Results and Discussion…………………………….………………………..25
3.4.1. Metastability of the δ modification of syndiotactic polystyrene…25
3.4.2. Magnitude of the thermal conductivity.…………………………...27
3.4.3. Anisotropy of the thermal conductivity…………………………...28
3.4.4. Influence of constraint patterns on the thermal conductivity……...29
3.4.5. Influence of chain packing on the thermal conductivity…………..30
3.5. Summary…………………………………………………………………….34
II3.6. References…………………………………………………………………..37
4. Properties of polyvinyl alcohol oligomers: a molecular dynamics study…………….39
4.1. Introduction…………………………………………………………………39
4.2. Computational Details………………………………………………………40
4.3. Results and Discussion……………………………………………………...42
4.3.1. Density, specific volume and distribution of the atoms…………..42
4.3.2. Relaxation and diffusion………………………………………….48
4.4. Summary…………………………………………………………………….55
4.5. References…………………………………………………………………...57
5. Study of the Soret effect in hydrocarbone chains/aromatic compound mixtures……..59
5.1. Introduction…………………………………………………………………59
5.2. Experimental details…………………………………………………………61
5.2.1 Sample preparation………………………………………………...61
5.2.2. Refractive index increment measurements………………………..62
5.2.3 TDFRS experiment and data analysis……………………………...63
5.3. Computational Details………………………………………………………63
5.4. Results and Discussion……………………………………………………...65
5.4.1. Experiment………………………………………………………...65
5.4.2.. Simulation………………………………………………………...69
5.5. Conclusions………………………………………………………………….73
5.6. References…………………………………………………………………...75
6: Summary………………………………………………………………………………77
References………………………………………………………………………..80
Publications………………………………………………………………………………81
Curriculum Vitae………………………………………………………………………...82

IIIList of Figures

Figure 2.1: Schematic drawing of a thermal diffusion forced Rayleigh scattering
(TDFRS) setup. The picture has been taken from previous publication [S. Wiegand, J.
Phys.-Condes. Matter 16 (10), R357 (2004)]……………….…………………………….7
Figure 2.2: Sketch of the (/∂∂nT) interferometer(the picture has been taken from P,x
previous publication [P. Polyakov, Ph.D. thesis, University of Twente, Enschede, the
Netherlands (2008)])………………………………………………………………………8
Figure 2.3: Illustration of the heat exchange algorithm for determination of the Soret
coefficient by non equilibrium simulation……………………………………………….11
Figure 3.1: The δ modification of syndiotactic polystyrene (sPS) viewed along the helix
axis (z direction)…………………………………………………………………………18
Figure 3.2: Different projections of the basic cell and its division into analysis slabs in x,
y and z directions, respectively. For the RNEMD simulations, the basic cell has been
replicated in the direction of the temperature gradient and heat flow: 3 times in x and z, 4
times in y direction, respectively………………………………………………………...18
Figure 3.3: Scheme of the different constraint patterns and assignment of semimolecular
groups. Constrained bonds are marked by thick solid lines, flexible bonds by thin dashed
lines. Semimolecular groups of atoms are encircled…………………………………….20
Figure 3.4: Density and temperature profiles of the same system (temperature gradient
and heat flux in z direction, time step 0.0005 ps, semimolecular velocity exchange every
0.25 ps, 8 constraint (Figure 3.3b), the average temperature of the system is 300K, which
for the RNEMD analysis has been divided into different numbers of slabs: (a) 12 slabs,
which is commensurate with the 48 monomers/chain in this direction: (b) 20 slabs, which
is incommensurate and leads not only to spurious density oscillations, but also to
nonlinearity artefacts in the temperature profile…………………………………………24
Figure 3.5: Thermal conductivity (Cartesian components) of sPS at 300 K as a function
of the density normalized by its equilibrium value at 300 K and 101.3 kPa: (a) δ form,
and (b) compact form…………………………………………………………………….33
IVFigure 4.1: Specific volume of melts of PVA oligomers as a function of the inverse chain
5,59length at T=300 K. The value of amorphous PVA at 298 K was put at 1/N = 0. This
5choice is based on the assumption that the PVA chains reported in the literature are
longer than the ones simulated here. Note that the N=1, 2 systems have been omitted in
the linear fit………………………………………………………………………………44
Figure 4.2: Specific volume of PVA oligomer melts as a function of the inverse chain
length at T=300, 400 K. In analogy to Figure 4.1 the N=1 and 2 data have been omitted in
the linear fit………………………………………………………………………………45
Figure 4.3: Radial distribution function between oxygen atoms in melts of PVA
oligomers with chain lengths N=1,2,3 (a) and N=5,7,10 (b) at 400 K…………………..46
Figure 4.4: Radial distribution function between methine carbon atoms (connected to
oxygen) in melts of PVA oligomers with chain lengths N=1,2,3 (a) and N=5,7,10 (b) at
400 K. In the inserts we have fragmented the radial distribution function into intra- and
intermolecular contributions. N=3 has been chosen in the first diagram, N=10 in the
second one………………………………………………………………………………..48
Figure 4.5: Double logarithmic representation of the gyration radius of PVA chains as a
function of the chain length (the error bar is the standard deviation)……………………48
Figure 4.6. Orientation correlation function of the O-H bond vector for melts of PVA
oligomers with the chain length N=1,2,3 (a) and N=5,7,10 (b) at 400 K. The insert in
figure (a) shows the orientation correlation functions for isopropanol (N=1) and 2,4-
pentanediol (N=2) at higher resolution. Note the logarithmic scale for the y-axis………50
Figure 4.7: Orientation correlation function for the bond vectors (O-H, O-C, CH-CH 2
[internal], CH-CH [end]) and the en