Free Energy and Surface Forces in polymer systems: Monte Carlo Simulation Studies

Abstract

The thesis is focused on two major subjects:



- Calculation of free energy is of great help in the study of any molecular system. The free energy determines phase behaviour of colloids and polymer solutions. It also controls the conformational properties of single macromolecules, e.g. DNA, proteins, copolymers. One of the most robust computer simulation techniques for free energy estimation is an Expanded Ensemble approach which is used throughout all the present work. Starting with a simple lattice polymer model, we develop and test an iterative procedure that makes the method automatic and accurate. Then we apply it to various polymer systems. The ideas behind a few similar approaches for overcoming rough free energy barriers lead to a non-equilibrium simulation method that yields e.g. the Gibbs free energy profile, G(V)=F(V)+pV. The latter is a direct route to phase diagrams which are invaluable when studying a thermodynamic system. This way we investigate the phase behaviour of constrained polymer systems.



- Surface force calculation: another application of the expanded ensemble is to equalize the chemical potential of a polymer solution confined to a planar pore while changing its width. Forces acting along and perpendicular to the surfaces are then obtained by usual means of statistical mechanics and from the thermodynamic relations, the surface free energy in particular. A number of different polymer systems were dealt with in this framework.

• author: Broukhno, Andrei
• supervisor: [unknown] [unknown]
• opponent: Prof. Toxwaerd, S., University of Copenhagen
• organization: Computational Chemistry
• publishing date: 2003
• type: Thesis
• publication status: published
• subject: Theoretical Chemistry
• keywords: polyelectrolytes, electrostatic interactions, phase transitions, colloidal stability, surface forces, Monte Carlo simulation, free energy evaluation, polyampholytes, Physical chemistry, Fysikalisk kemi
• pages: 155 pages
• defense location: Lecture Hall ``G'' at the Chemical Center
• defense date: 2003-05-22 10:15:00
• ISBN: 91-628-5576-X
• language: English
• LU publication?: yes
• additional info: Article: 1. P. N. Vorontsov-Velyaminov, A. V. Broukhno, T. V. Kuznetsova, and A. P. Lyubartsev, "Free Energy Calculations by Expanded Ensemble Method for Lattice and Continuous Polymers", J. Phys. Chem. 100, 1153-1158 (1996) Article: 2. P. N. Vorontsov-Velyaminov, D. A. Ivanov, S. D. Ivanov and A. V. Broukhno, "Expanded Ensemble Monte Carlo Calculations of Free Energy for Closed, Stretched and Confined Lattice Polymers", Colloids and Surfaces: A 148, 171-177 (1999) Article: 3. A. V. Broukhno, B. Jönsson, T. Åkesson and P. N. Vorontsov-Velyaminov, "Depletion and Bridging Forces in Polymer Systems: Monte Carlo Simulations at Constant Chemical Potential", J. Chem. Phys. 113, 5493-5501 (2000) Article: 4. A. V. Broukhno, M. O. Khan, T. Åkesson, and B. Jönsson, "Polyampholyte Induced Repulsion Between Charged Surfaces: Monte Carlo Simulation Studies", Langmuir 18, 6429-6436 (2002) Article: 5. B. Jönsson, A. V. Broukhno, J. Forsman, and T. Åkesson, "Depletion and Structural Forces in Confined Polyelectrolyte solutions", Submitted for publication to Langmuir Article: 6. J. Forsman, A. V. Broukhno, B. Jönsson, and T. Åkesson, "Surface Forces in Confined Polymer Fluids: a Comparison between Simulations and Density Functional Theory", Submitted for publication to Europhysics Letters. Article: 7. A. V. Broukhno, T. Åkesson, B. Jönsson, and J. Forsman, "Phase Equilibria in Confined Oligomer Fluids from Monte Carlo Simulations", Submitted for publication to Physical Review The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Theoretical Chemistry (S) (011001039)
• id: ac792487-5b1f-4302-a6a5-9f1a19343040 (old id 465739)
• date added to LUP: 2016-04-04 12:05:36
• date last changed: 2018-11-21 21:08:56