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Off-equilibrium response of grafted polymer chains subject to a variable rate of compression
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 24, 11757-11765 p.Article in journal (Refereed) Published
Abstract [en]

We present Brownian dynamics simulations of single grafted semiflexible chains (i.e., "polymer mushrooms'') with varying persistence lengths, intra-chain interactions, and subject to confinement. The results from different rates of compression are presented in the cases of an approaching infinite plane and a paraboloid tip. We discuss the different behaviour observed for grafted chains with strong and weak self-attraction (i.e., "hard'' and "soft'' polymer mushrooms). In both cases the effect on the size and shape is more pronounced for a slow compression rate, especially for "hard mushrooms''. We have also studied the relaxation of the chain while the compressing plane is maintained, and when it is removed suddenly. We find that the response depends strongly on the time allowed for relaxation in the compressed state. When using instead a paraboloid tip, the overall effects are similar yet less pronounced because the chain can dodge the confining object via an "escape transition.''

Place, publisher, year, edition, pages
2011. Vol. 13, no 24, 11757-11765 p.
National Category
Natural Sciences Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-155223DOI: 10.1039/c1cp20462aISI: 000291395200037OAI: oai:DiVA.org:uu-155223DiVA: diva2:425579
Available from: 2011-06-21 Created: 2011-06-20 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Brownian Dynamics Simulations of Macromolecules: Algorithm Development and Polymers under Confinement
Open this publication in new window or tab >>Brownian Dynamics Simulations of Macromolecules: Algorithm Development and Polymers under Confinement
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis I have used computer simulations to study the structure and dynamics of grafted polymers during confinement. These systems are of importance for understanding e.g. colloidal stability and surface coatings. We have used Brownian dynamics simulations with the polymers modeled as discrete wormlike chains allowing for a variable persistence length as well as different non-bonded interactions. The size and shape of the chains are characterized by the radius of gyration and the degree of oblateness/prolateness, and the entanglement is followed by calculating the mean overcrossing number. Starting in the dilute regime with a single polymer mushroom we have investigated how the rate of compression and solvent quality effects the behaviour of a compressed chain. In the brush regime, we investigated how the surface coverage effects the behaviour during compression. For low coverages the chains have the possibilty to increase their lateral extension during confinement but in general, the chains have a low inter-entanglement, as they strive to keep their integrity during the confinement process.

To go from a polymer brush to the construction of a connected network, we have developed a method to construct a closed network without using periodic boundary conditions by building the network on a sphere in R4. In this way we avoid the restrictions of periodicity at the cell boundaries. We finally also show how to develop the idea of using spherical boundary conditions, by presenting a novel algorithm for simulating diffusion on a spherical surface. The method is more stable and allows for larger time steps, compared to commonly used methods in computer simulations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 58 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 937
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-173435 (URN)978-91-554-8377-7 (ISBN)
Public defence
2012-06-04, Å2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-05-14 Created: 2012-04-24 Last updated: 2014-12-30Bibliographically approved

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Sundberg, Jill

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