Kurt Kremer

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Organization: Max-Planck-Institut für Polymerforschung , Germany

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Polymer

Chemicals
References

Reply to the ‘Comment on “Relating side chain organization of PNIPAm with its conformation in aqueous methanol”’ by A. Pica and G. Graziano, Soft Matter, 2017, 13, DOI: 10.1039/C7SM01065F

Co-reporter:Debashish Mukherji;Manfred Wagner;Mark D. Watson;Svenja Winzen;Tiago E. de Oliveira;Carlos M. Marques

Soft Matter (2005-Present) 2017 vol. 13(Issue 42) pp:7701-7703

Publication Date(Web):2017/11/01

DOI:10.1039/C7SM01880K

We have recently proposed preferential binding by a cosolvent as the mechanism for chain collapse under co-non-solvency. Here we summarise our earlier works and provide further evidence that alcohol preferentially binds to PNIPAm, forming cosolvent bridges, and thus drives the transition. We also clarify some of the common misconceptions evoked in this debate with Pica and Graziano (PG), reinforcing the arguments of our earlier reply-comment [Soft Matter, 2017, 13, 2292] and published works.

Reply to the ‘Comment on “Relating side chain organization of PNIPAm with its conformation in aqueous methanol”’ by N. van der Vegt and F. Rodriguez-Ropero, Soft Matter, 2017, 13, DOI: 10.1039/C6SM02139E

Co-reporter:Debashish Mukherji;Manfred Wagner;Mark D. Watson;Svenja Winzen;Tiago E. de Oliveira;Carlos M. Marques

Soft Matter (2005-Present) 2017 vol. 13(Issue 12) pp:2292-2294

Publication Date(Web):2017/03/22

DOI:10.1039/C7SM00041C

In a comment van der Vegt and Rodriguez-Ropero (vdVRR) challenged our explanation of the co-non-solvency effect of PNIPAm in aqueous methanol solutions. They argue, based on a careful selection of published studies including some of their own, that direct repulsions between the different constituents are sufficient to understand this phenomenon. According to vdVRR, the emerging view of entropic collapse, put forward by Flory (1910–1985) to explain common polymers in poor solvents, would be enough to explain co-non-solvency. In this reply we attempt to bring this discussion into firmer grounds. We provide a more comprehensive view of available experimental, numerical and theoretical results and review basic concepts of physical chemistry and of statistical mechanics of polymer collapse that show how methanol mediated attractions between chain monomers are required to understand this fascinating behavior.

Comparison of two coarse-grained models of cis-polyisoprene with and without pressure correction

Co-reporter:Takahiro Ohkuma, Kurt Kremer

Polymer 2017 Volume 130(Volume 130) pp:

Publication Date(Web):9 November 2017

DOI:10.1016/j.polymer.2017.09.062

•Equilibrium pressure and compressibility are different in the two models.•Two models show the same Kuhn length and entanglement molecular weight.•Two models show the same stress relaxation function and viscosity.We investigate two coarse-grained models of a cis-polyisoprene melt. The bonded interactions which are used in both models are derived by Boltzmann inversion of the probability distributions of the bonded variables in a single chain simulation. The non-bonded interactions are derived by an iterative Boltzmann inversion method in the melt state with pressure correction in a model and without in the other model. In our mapping rule, two or three carbons are grouped into coarse-grained beads. The trade-off relationship between pressure and compressibility is observed in the coarse-grained models. Since the relaxation dynamics of the coarse-grained models are accelerated by the smoothed potentials, single numerical factors are introduced to rescale the time scale of the coarse-grained models, respectively. The factors of the two models are in the same order but the model with pressure correction displays larger acceleration than the other. It is found that the stress relaxation function near equilibrium and the nonlinear viscosity under steady shear are essentially the same between the two coarse-grained models in the rescaled time scales despite of their different equilibrium pressures. We also study the dependency of the rescaling factors on the chain length of the polymer. The rescaling factors increase with increasing the chain length and exponentially saturates to certain values around 100 monomers in chains.Download high-res image (212KB)Download full-size image

Adaptive Resolution Simulations with Self-Adjusting High-Resolution Regions

Co-reporter:Karsten Kreis, Raffaello Potestio, Kurt Kremer, and Aoife C. Fogarty

Journal of Chemical Theory and Computation 2016 Volume 12(Issue 8) pp:4067-4081

Publication Date(Web):July 6, 2016

DOI:10.1021/acs.jctc.6b00440

In adaptive resolution simulations, different regions of a simulation box are modeled with different levels of detail. Particles change their resolution on-the-fly when traveling from one subregion to the other. This method is particularly useful for studying multiscale systems in which effects on a broad range of length and time scales play a role. Until now, the geometry of the high-resolution region has been limited to simple geometries of spherical, cuboid, or cylindrical form, whose shape does not change during the simulation. However, many phenomena involve changes in size and shape of system components, for example, protein folding, polymer collapse, nucleation, and crystallization. In this work, we develop a scheme that uses a series of overlapping spheres to allow for an arbitrary division of space into domains of different levels of resolution. Furthermore, the geometry is automatically adjusted on-the-fly during the simulation according to changes in size and shape of, for example, a solvated macromolecule within the high-resolution region. The proposed approach is validated on liquid water. We then simulate the folding of an atomistically detailed polypeptide solvated in a shell of atomistic water that changes shape as the peptide conformation changes. We demonstrate that the peptide folding process is unperturbed by the use of our methodology.

Effect of Mesoscale Ordering on the Density of States of Polymeric Semiconductors

Co-reporter:Patrick Gemünden;Carl Poelking;Kostas Daoulas;Denis Andrienko

Macromolecular Rapid Communications 2015 Volume 36( Issue 11) pp:1047-1053

Publication Date(Web):

DOI:10.1002/marc.201400725

Why does high pressure destroy co-non-solvency of PNIPAm in aqueous methanol?

Co-reporter:Tiago E. de Oliveira, Paulo A. Netz, Debashish Mukherji and Kurt Kremer

Soft Matter 2015 vol. 11(Issue 44) pp:8599-8604

Publication Date(Web):27 Aug 2015

DOI:10.1039/C5SM01772F

It is well known that poly(N-isopropylacrylamide) (PNIPAm) exhibits an interesting, yet puzzling, phenomenon of co-non-solvency. Co-non-solvency occurs when two competing good solvents for PNIPAm, such as water and alcohol, are mixed together. As a result, the same PNIPAm collapses within intermediate mixing ratios. This complex conformational transition is driven by preferential binding of methanol with PNIPAm. Interestingly, co-non-solvency can be destroyed when applying high hydrostatic pressures. In this work, using a large scale molecular dynamics simulation employing high pressures, we propose a microscopic picture behind the suppression of the co-non-solvency phenomenon. Based on thermodynamic and structural analysis, our results suggest that the preferential binding of methanol with PNIPAm gets partially lost at high pressures, making the background fluid reasonably homogeneous for the polymer. This is consistent with the hypothesis that the co-non-solvency phenomenon is driven by preferential binding and is not based on depletion effects.

Cover Picture: Macromol. Theory Simul. 52015

Co-reporter:Livia A. Moreira;Guojie Zhang;Franziska Müller;Torsten Stuehn

Macromolecular Theory and Simulations 2015 Volume 24( Issue 5) pp:

Publication Date(Web):

DOI:10.1002/mats.201570014

Direct Equilibration and Characterization of Polymer Melts for Computer Simulations

Co-reporter:Livia A. Moreira;Guojie Zhang;Franziska Müller;Torsten Stuehn

Macromolecular Theory and Simulations 2015 Volume 24( Issue 5) pp:419-431

Publication Date(Web):

DOI:10.1002/mats.201500013

Topological constraints due to chain connectivity and uncrossability greatly impact the long time dynamics and rheology of high molecular weight polymer melts. Computer simulations to study properties of such melts are very advantageous, since perfect control of molecular conformation and melt morphology is available. We present a methodology to prepare well-equilibrated polymer melts which only requires local relaxation. The approach efficiently leads to equilibrated ensembles of bead-spring polymer melts of 1 000 chains of up to 2 000 beads, which correspond to 24 (fully flexible) and 45 entanglement lengths (semi-flexible chains). Entanglements are identified by a primitive path analysis and a master curve of the entanglement lengths for different chain and persistence lengths is presented.

Equilibration of High Molecular Weight Polymer Melts: A Hierarchical Strategy

Co-reporter:Guojie Zhang, Livia A. Moreira, Torsten Stuehn, Kostas Ch. Daoulas, and Kurt Kremer

ACS Macro Letters 2014 Volume 3(Issue 2) pp:198

Publication Date(Web):January 30, 2014

DOI:10.1021/mz5000015

A strategy is developed for generating equilibrated high molecular weight polymer melts described with microscopic detail by sequentially backmapping coarse-grained (CG) configurations. The microscopic test model is generic but retains features like hard excluded volume interactions and realistic melt densities. The microscopic representation is mapped onto a model of soft spheres with fluctuating size, where each sphere represents a microscopic subchain with Nb monomers. By varying Nb, a hierarchy of CG representations at different resolutions is obtained. Within this hierarchy, CG configurations equilibrated with Monte Carlo at low resolution are sequentially fine-grained into CG melts described with higher resolution. A Molecular Dynamics scheme is employed to slowly introduce the microscopic details into the latter. All backmapping steps involve only local polymer relaxation; thus, the computational efficiency of the scheme is independent of molecular weight, being just proportional to system size. To demonstrate the robustness of the approach, microscopic configurations containing up to n = 1000 chains with polymerization degrees N = 2000 are generated and equilibration is confirmed by monitoring key structural and conformational properties. The extension to much longer chains or branched polymers is straightforward.

Macromol. Chem. Phys. 2/2013

Co-reporter:Guojie Zhang;Kostas C. Daoulas

Macromolecular Chemistry and Physics 2013 Volume 214( Issue 2) pp:

Publication Date(Web):

DOI:10.1002/macp.201370005

A New Coarse Grained Particle-To-Mesh Scheme for Modeling Soft Matter

Co-reporter:Guojie Zhang;Kostas C. Daoulas

Macromolecular Chemistry and Physics 2013 Volume 214( Issue 2) pp:214-224

Publication Date(Web):

DOI:10.1002/macp.201200520

Abstract

A recently proposed model of high-molecular-weight polymers is employed to develop a grid-based Monte Carlo method for efficient modeling of dense systems, for example, melts. The polymers are described as chains of soft spheres with fluctuating size. The spheres correspond to Gaussian density distributions of the microscopic segments and represent whole subchains. Their coordinates and radii are defined in continuum space and simple potentials keep the chain connectivity. A density functional defines the nonbonded interactions by mapping the density distributions onto a grid, without a neighbor list. The high accuracy of the scheme is demonstrated by comparing with data obtained from the standard potential-based formulation of the model. Contrary to most lattice models, the method allows for NPT simulations.

Preferential Solvation of Triglycine in Aqueous Urea: An Open Boundary Simulation Approach

Co-reporter:Debashish Mukherji, Nico F. A. van der Vegt , Kurt Kremer

Journal of Chemical Theory and Computation 2012 Volume 8(Issue 10) pp:3536-3541

Publication Date(Web):July 9, 2012

DOI:10.1021/ct300253n

Solvation free energies of peptides in water decrease with increasing urea concentration and therefore lead to increased solubility. In this work, we study the solvation thermodynamics of a triglycine in aqueous urea solutions at room temperature T = 300 K. We perform our analysis within the framework of the Kirkwood–Buff theory of liquid mixtures, developed for open systems. For this purpose, we use a recently proposed approach to study liquid mixtures within an “effective” open boundary simulation scheme (AdResS). We couple a small open boundary all-atom (explicit) region to a much larger coarse-grained particle reservoir. This coupling allows the free exchange of particles in thermodynamic equilibrium. Our approach preserves correct particle fluctuations that are important for studying the concentration driven conformational transition of (bio)molecules.

Derivation of Coarse Grained Models for Multiscale Simulation of Liquid Crystalline Phase Transitions

Co-reporter:Biswaroop Mukherjee, Luigi Delle Site, Kurt Kremer, and Christine Peter

The Journal of Physical Chemistry B 2012 Volume 116(Issue 29) pp:8474-8484

Publication Date(Web):April 4, 2012

DOI:10.1021/jp212300d

We present a systematic derivation of a coarse grained (CG) model for molecular dynamics (MD) simulations of a liquid crystalline (LC) compound containing an azobenzene mesogen. The model aims at a later use in a multiscale modeling approach to study liquid crystalline phase transitions that are (photo)induced by the trans/cis photoisomerization of the mesogen. One of the major challenges in the coarse graining process is the development of models that are for a given chemical system structurally consistent with for example an all-atom reference model and reproduce relevant thermodynamic properties such as the LC phase behavior around the state point of interest. The reduction of number of degrees of freedom makes the resulting coarse models by construction state point dependent; that is, they cannot easily be transferred to a range of temperatures, densities, system compositions, etc. These are significant challenges, in particular if one wants to study LC phase transitions (thermally or photoinduced). In the present paper we show how one can systematically derive a CG model for a LC molecule that is highly consistent with an atomistic description by choosing an appropriate state point for the reference simulation. The reference state point is the supercooled liquid just below the smectic-isotropic phase transition which is characterized by a high degree of local nematic order while being overall isotropic. With the resulting CG model it is possible to switch between the atomistic and the CG levels (and vice versa) in a seamless manner maintaining values of all the relevant order parameters which describe the smectic A (smA) state. This model will allow us in the future to link large length scale and long time scale CG simulations of the LC state with chemically accurate QM/MM simulations of the photoisomerization process.

Multiscale modeling of soft matter: scaling of dynamics

Co-reporter:Dominik Fritz, Konstantin Koschke, Vagelis A. Harmandaris, Nico F. A. van der Vegt and Kurt Kremer

Physical Chemistry Chemical Physics 2011 vol. 13(Issue 22) pp:10412-10420

Publication Date(Web):05 Apr 2011

DOI:10.1039/C1CP20247B

Many physical phenomena and properties of soft matter systems are characterized by an interplay of interactions and processes that span a wide range of length- and time scales. Computer simulation approaches require models, which cover these scales. These are typically multiscale models that combine and link different levels of resolution. In order to reach mesoscopic time- and length scales, necessary to access material properties, coarse-grained models are developed. They are based on microscopic, atomistic descriptions of systems and represent these systems on a coarser, mesoscopic level. While the connection between length scales can be established immediately, the link between the different time scales that takes into account the faster dynamics of the coarser system cannot be obtained directly. In this perspective paper we discuss methods that link the time scales in structure based multiscale models. Concepts which try to rigorously map dynamics of related models are limited to simple model systems, while the challenge in soft matter systems is the multitude of fluctuating energy barriers of comparable height. More pragmatic methods to match time scales are applied successfully to quantitatively understand and predict dynamics of one-component soft matter systems. However, there are still open questions. We point out that the link between the dynamics on different resolution levels can be affected by slight changes of the system, as for different tacticities. Furthermore, in two-component systems the dynamics of the host polymer and of additives are accelerated very differently.

Fluctuating soft-sphere approach to coarse-graining of polymer models

Co-reporter:Thomas Vettorel, Gerhard Besold and Kurt Kremer

Soft Matter 2010 vol. 6(Issue 10) pp:2282-2292

Publication Date(Web):01 Apr 2010

DOI:10.1039/B921159D

We introduce a coarse-grained model for the simulation of the statistical properties of polymeric systems where collections of chain segments are represented by connected soft spheres of fluctuating size. A generic bead–spring model is considered as a test case for this coarse-graining approach. The effective interactions between the soft spheres and the effective free energy that governs the size distribution of soft spheres are determined using analytical calculations or empirical expressions, leading to relatively simple functional forms that facilitate implementation in the simulation code. The validity of this coarse-graining approach is tested on a variety of systems ranging from ideal chains to dilute solutions and melts. The scheme allows to vary the spatial range of coarse-graining in a flexible and consistent way, and turns out to be particularly efficient for polymer melts. The equilibrium properties of the coarse-grained model agree with those of the original bead–spring model. As the coarse graining does not conserve entanglements, the dynamics is restricted to Rouse-like and the considerably accelerated coarse-grained dynamics suggests this approach as particularly promising for the equilibration of large long-chain polymer melts and mixtures.

Macromol. Theory Simul. 1/2010

Co-reporter:Thomas Vettorel

Macromolecular Theory and Simulations 2010 Volume 19( Issue 1) pp:

Publication Date(Web):

DOI:10.1002/mats.201090001

Development of Entanglements in a Fully Disentangled Polymer Melt

Co-reporter:Thomas Vettorel

Macromolecular Theory and Simulations 2010 Volume 19( Issue 1) pp:44-56

Publication Date(Web):

DOI:10.1002/mats.200900065

Reply to Comment on “Entangled Polymer Melts: Relation between Plateau Modulus and Stress Autocorrelation Function”

Co-reporter:Won Bo Lee, Jonathan Halverson and Kurt Kremer

Macromolecules 2010 Volume 43(Issue 8) pp:3984-3985

Publication Date(Web):March 22, 2010

DOI:10.1021/ma1004502

Multiscale simulation of soft matter systems – from the atomistic to the coarse-grained level and back

Co-reporter:Christine Peter and Kurt Kremer

Soft Matter 2009 vol. 5(Issue 22) pp:4357-4366

Publication Date(Web):19 Aug 2009

DOI:10.1039/B912027K

Many physical phenomena and properties of soft matter systems such as synthetic or biological materials are governed by interactions and processes on a wide range of length- and time-scales. Computer simulation approaches that are targeted at questions in these systems require models which cover these scales and the respective levels of resolution. Multiscale simulation methods combine and systematically link several simulation hierarchies so that they can address phenomena at multiple levels of resolution. In order to reach the mesoscopic time- and length-scales important for many material properties, methods that bridge from the atomistic (microscopic) to a coarser (mesocopic) level are developed. Here, we review coarse-grained simulation models that are linked to a higher resolution atomistic description. In particular, we focus on structure-based coarse-graining methods which are used for a variety of soft matter problems – ranging from structure-formation in amorphous polymers to biomolecular aggregation. It is shown that by coarse-grained simulation in combination with an efficient backmapping methodology one can obtain well-equilibrated long time- and large length-scale atomistic structures of polymeric melts or biomolecular aggregates which can be used for comparison to experimental data. Methodological aspects are addressed such as the question of the time-scales and dynamics in the different simulation hierarchies and an outlook to future challenges in the area of resolution exchange approaches and adaptive resolution models is presented.

Entangled Polymer Melts: Relation between Plateau Modulus and Stress Autocorrelation Function

Co-reporter:Won Bo Lee and Kurt Kremer

Macromolecules 2009 Volume 42(Issue 16) pp:6270-6276

Publication Date(Web):July 20, 2009

DOI:10.1021/ma9008498

Stress autocorrelation functions (SAF) of entangled polymer melts are calculated by coarse-grained molecular dynamics (MD) simulations. We show that time-averaged stresses reduce the strong noise in SAFs while still capturing most relevant relaxations of the chains. Plateau values of the SAF compare well with plateau values predicted from the entanglement length evaluated via primitive path analysis (PPA) and from experiment (where available). Three types of polymer models are studied: a flexible bead spring model, a semiflexible bead spring model, and a coarse grained bisphenol A-polycarbonate (BPAPC) model. This approach provides a straightforward way to analyze rheological properties of polymer melts on the fly during a simulation.

Comparison Between Coarse-Graining Models for Polymer Systems: Two Mapping Schemes for Polystyrene

Co-reporter:Dirk Reith;Nico F. A. van der Vegt;Vagelis A. Harmaris

Macromolecular Chemistry and Physics 2007 Volume 208(Issue 19‐20) pp:2109-2120

Publication Date(Web):21 AUG 2007

DOI:10.1002/macp.200700245

We present a detailed study of a new, optimized coarse-grained (CG) model of polystyrene (PS) and compare it with a recently published one (Harmandaris et al., Macromolecules2006, 39, 6708). By implementing a different mapping scheme, the new model, augmented with softer nonbonded interactions, better reproduces the local chain conformations and melt packing observed in atomistic simulations of atactic PS. Both models properly predict the bonded distributions and are capable of simulating different tacticities without needing sidegroups. Both CG models fit dynamic data from long atomistic simulations after determining the scale factor for the simulation time. Together with a rigorous back-mapping procedure from the mesoscopic to atomistic description, this opens up a very feasible way for generating very long atomistic trajectories.

Aggregation and vesiculation of membrane proteins by curvature-mediated interactions

Co-reporter:Benedict J. Reynwar, Gregoria Illya, Vagelis A. Harmandaris, Martin M. Müller, Kurt Kremer & Markus Deserno

Nature 2007 447(7143) pp:461

Publication Date(Web):2007-05-24

DOI:10.1038/nature05840

Membrane remodelling1, 2, 3, 4, 5 plays an important role in cellular tasks such as endocytosis, vesiculation and protein sorting, and in the biogenesis of organelles such as the endoplasmic reticulum or the Golgi apparatus. It is well established that the remodelling process is aided by specialized proteins that can sense4 as well as create6 membrane curvature, and trigger tubulation7, 8, 9 when added to synthetic liposomes. Because the energy needed for such large-scale changes in membrane geometry significantly exceeds the binding energy between individual proteins and between protein and membrane, cooperative action is essential. It has recently been suggested10, 11 that curvature-mediated attractive interactions could aid cooperation and complement the effects of specific binding events on membrane remodelling. But it is difficult to experimentally isolate curvature-mediated interactions from direct attractions between proteins. Moreover, approximate theories predict repulsion between isotropically curving proteins12, 13, 14, 15. Here we use coarse-grained membrane simulations to show that curvature-inducing model proteins adsorbed on lipid bilayer membranes can experience attractive interactions that arise purely as a result of membrane curvature. We find that once a minimal local bending is realized, the effect robustly drives protein cluster formation and subsequent transformation into vesicles with radii that correlate with the local curvature imprint. Owing to its universal nature, curvature-mediated attraction can operate even between proteins lacking any specific interactions, such as newly synthesized and still immature membrane proteins in the endoplasmic reticulum.

Long time atomistic polymer trajectories from coarse grained simulations: bisphenol-A polycarbonate

Co-reporter:Berk Hess, Salvador León, Nico van der Vegt and Kurt Kremer

Soft Matter 2006 vol. 2(Issue 5) pp:409-414

Publication Date(Web):29 Mar 2006

DOI:10.1039/B602076C

Based on coarse grained simulations of a specially adapted model for bisphenol-A polycarbonate (BPA-PC) we generate by inverse mapping, i.e. the reintroduction of chemical details, well equilibrated all-atom conformations and time trajectories of dense polymeric melts for up to 7.8 µs. This is several orders of magnitude more than any direct all-atom simulations have reached so far. These polymer melts contain up to 68600 atoms in n = 100 chains of molecular weight M = 5217. By comparison with short all-atom simulations we show that these trajectories are physically meaningful, providing us with a powerful tool to compare long time simulations to experiments, which probe specific local dynamics on long time scales, such as NMR relaxation.

Cover Picture: Macromol. Symp. 237/2006

Co-reporter:Bernward A. Mann;Christian Holm

Macromolecular Symposia 2006 Volume 237(Issue 1) pp:

Publication Date(Web):18 APR 2006

DOI:10.1002/masy.200690077

The Swelling Behavior of Charged Hydrogels

Co-reporter:Bernward A. Mann;Christian Holm

Macromolecular Symposia 2006 Volume 237(Issue 1) pp:90-107

Publication Date(Web):18 APR 2006

DOI:10.1002/masy.200650511

Summary: We describe recent advances obtained in understanding the microscopic interplay of a charged hydrogel with its confined mobile counterions. Results of extensive computer simulations are compared to simple scaling descriptions for various solvent conditions. We will briefly discuss our simulation package ESPResSo which was used to perform the simulations. We demonstrate why simple scaling theories suffice to adequately describe the swelling behavior of these systems despite their enormous complexity. We will conclude with a presentation of ongoing results for polyelectrolyte networks under poor solvent conditions.

Entangled polymer systems

Co-reporter:Kurt Kremer, Sathish K. Sukumaran, Ralf Everaers, Gary S. Grest

Computer Physics Communications 2005 Volume 169(1–3) pp:75-81

Publication Date(Web):1 July 2005

DOI:10.1016/j.cpc.2005.03.019

Topological constraints, referred to as entanglements in the literature, dominate the viscoelastic behavior of high molecular weight polymeric liquids. To give a microscopic foundation of the phenomenological tube models which successfully describe this behavior, we have recently introduced a method for identifying the so-called primitive path mesh that characterizes the microscopic topological state of (computer generated) conformations of long-chain polymer networks, melts and solutions. Here we give a short account of this approach and discuss some applications.

Computer Simulations of the “Hairy Rod” Model

Co-reporter:Hans Jörg Limbach;Christian Holm

Macromolecular Chemistry and Physics 2005 Volume 206(Issue 1) pp:

Publication Date(Web):27 DEC 2004

DOI:10.1002/macp.200400286

Summary: Using extensive Molecular Dynamics simulations we study the behavior of very rigid polyelectrolytes with hydrophobic side chains that are known to form cylindrical micelles in aqueous solution. We investigate the stability of such micelles with respect to hydrophobicity, Coulomb interaction, and micellar size. We show that for the parameter range relevant for poly(p-phenylene sulfonate)s (PPP) one finds a stable finite micellar size close to the experimental parameter region. We also point out that our model has some similarities to DNA solutions with added condensing agents, hinting to the possibility that the size of DNA aggregates is under certain circumstances thermodynamically limited.

Conformations and solution structure of polyelectrolytes in poor solvent

Co-reporter:Christian Holm;Hans Jörg Limbach

Macromolecular Symposia 2004 Volume 211(Issue 1) pp:43-54

Publication Date(Web):11 MAY 2004

DOI:10.1002/masy.200450703

Using extensive Molecular Dynamics (MD) simulations we study the behavior of polyelectrolytes in poor solvents, where we take explicitely care of the counterions. The resulting pearl-necklace structures are subject to strong conformational fluctuations, only leading to small signatures in the form factor, which is a severe obstacle for experimental observations. In addition we study how the necklace collapses as a function of Bjerrum length. At last we demonstrate that the position of the first peak in the inter-chain structure factor varies with the monomer density close to for all densities. This is in strong contrast to polyelectrolyte solutions in good solvent.

Multiscale modeling of soft matter: scaling of dynamics

Co-reporter:Dominik Fritz, Konstantin Koschke, Vagelis A. Harmandaris, Nico F. A. van der Vegt and Kurt Kremer

Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 22) pp:NaN10420-10420

Publication Date(Web):2011/04/05

DOI:10.1039/C1CP20247B