Computational investigation of chain dynamics in architecturally complex polymers

We investigate the chain dynamics in the polymer melts with complex architecture by means of molecular dynamics simulations. Our study is focused on the following architecturally complex polymers: T- and Y-shaped asymmetric stars, symmetric stars, mixtures of Tshaped asymmetric stars and linear chains, H-polymers, combs and Cayley trees. Dynamics in these architectures is strongly influenced by the presence of one or more branchpoints. The overall chain dynamics in branched structures is slowed down comparing to the linear chain and the relaxation of these materials extend over several time decades. Extensive molecular dynamics simulations allow us to study the relaxation processes ocurring in the branched polymer melts at the molecular level. We pay particular attention to the role of the branchpoint in the dynamics of these systems. Our simulations reveal details about the branchpoint motion that can be further compared to the theoretical hypotheses, experimental data and finally introduced in the predictions of the viscoelastic properties of the industrially produced materials. The time evolutions of the mean squared displacements of the particular molecular segments confirm that the arm retraction is the main relaxation mechanism in symmetric systems, i.e. symmetric stars and Cayley trees. In these systems the branchpoint remains localized during the whole simulation time. We study the role of constraint release on the branchpoint dynamics and compare the simulation results with a theoretical model. The fluctuations of the branchpoint at time scales smaller than the Rouse time τR are affected by the early tube dilation process that leads to a weaker branchpoint localization than expected. After the incorporation of the early and late tube dilation processes quantified from the simulation data into the theoretical model, we were able to fully describe the branchpoint dynamics at the times smaller than τR. After the relaxation of the short side arms in the asymmetric structures the arms act as sources of friction and the whole molecule can be described as an effective linear chain. We studied the diffusion of the branchpoint after the arm relaxation. The calculation of the diffusion constant involves the knowledge about the arm relaxation, dilution of the tube and the friction related to the reptation of the molecule. We estimated these observables from the simulations and tested theoretical hypotheses used for the prediction of the branchpoint diffusive behaviour in experimental studies of branched polymer melts. We perform a detailed analysis of the branchpoint trajectories and present a robust method for finding regions of strong localization. We characterize the time and length scales for the branchpoint motion between traps of localization, and discuss the consequences for the interpretation of the long-time branchpoint motion dynamics proposed by hierarchical tube models.This thesis would have not been possible without the financial support from projects FP7-PEOPLE-2007-1-1-ITN (DYNACOP, EU), MAT2012-31088 (Spain) and IT654-13 (GV, Spain). I would like to acknowledge the programs PRACE, HPC-Europa2 and ESMI (EU), and ICTS (Spain) for generous allocation of CPU time at GENCI (France), HLRS and FZJ-JSC (Germany) and CESGA (Spain).Peer Reviewe

Studium perzistenční délky lineárních polyelektrolytů v roztocích

Department of Physical and Macromolecular ChemistryKatedra fyzikální a makromol. chemieFaculty of SciencePřírodovědecká fakult

Lineární semiflexibilní polyelektrolyty v roztocích

Název: Lineární semiflexibilní polyelektrolyty v roztocích Řešitel: Petra Bačová Ústav: Katedra fyzikální a makromolekulární chemie Školitel: Doc. Ing. Zuzana Limpouchová, CSc. E-mail školitele: [email protected] Konzultant: Mgr. Peter Košovan, PhD. Abstrakt: V předložené diplomové práci jsem se zabývala využitím MD simulací při studiu chování nabitých polymerů (polyelektrolytů) v roztocích. Velká část polyelektrolytových řetězců je semiflexibilní a narozdíl od neutrálních polymerů můžeme jejich ohebnost ovlivňovat kvalitou rozpouštědla, například změnou iontové síly. Flexibilitu řetězce můžeme popsat pomocí persistentní délky. Diplomová práce ukazuje, jak je možné vyjádřit persistentní délku z orientační korelační funkce, jejíž hodnota pro studovaný systém klesá dvojexpo- nenciálně. To znamená, že ohebnost řetězce lze popsat dvěma příspěvky, přičemž v diplo- mové práci se zabývám zejména jedním znich, který lze vyjádřit pomocí elektrostatické persistentní délky. Vliv přidané soli na konformaci řetězce je studován v rámci Debye- Hückelovy aproximace. Výsledky MD simulací jsou porovnány s OSF teorií a s variačními výpočty podle Manghiho a Netze. Předložená práce popisuje...Title: Linear semiflexible polyelectrolytes in solutions Author: Petra Bačová Department: Faculty of Science, Charles University in Prague Supervisor: Doc. Ing. Zuzana Limpouchová, CSc. Supervisor's e-mail address: [email protected] Consultant: Mgr. Peter Košovan, PhD. Abstract: In this thesis I used the Molecular dynamics simulations for study of charged polymers (polyelectrolytes) and their behaviour in solutions. Wide range of polyelectrolytes are se- miflexible and in contrast to neutral polymers it is possible to influence their stiffness by changing the properties of solution as for example ionic strength. The chain flexibility may be characterized by the persistence length. Thesis explains how to express the persistence length from orientational correlation function which shows the double exponential decay. Two contributions to chain stiffness are discussed and the interest is concentrated around electrostatic persistence length which seems to be scale dependent. An effect of added salt on the chain conformation is studied. Salt is treated implicitly within the Debye-Hückel approximation. The results are confronted with OSF theory and the conclusions of vari- ational calculations of Maghi and Netz. The presented thesis describes the conformational behaviour of polyelectrolytes in salty solutions,...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Dieudonné ako príklad nového antisemitizmu vo Francúzsku

This bachelor thesis is aimed at specific character of the new anti-Semitism in France and concrete elements that differ the new wave from the old one. This topic is very up to date in today's France because of significant increase of anti-Semitic crimes and growing numbres of jews emigrating to Israel. Three main differences which I explore in my thesis are : connection between new anti-Semitism and moslim immigrants, overlapping anti-Semitism with anti-Zionism and shift of anti-Semitism on the political spetrum. Second part of my thesis is study of artistic production of Dieudonné M'bala M'bala, french entertainer known for his controversial statements. In his political and artistic career I am trying to find aspects of new anti-Semitism mentioned in the first part.Práca sa zameriava na objasnenie špecifických znakov nového antisemitizmu vo Francúzsku a jeho odlíšenie od predošlých vĺn antisemitizmu. Aktuálnosť témy spočíva v značnom náraste antisemitsky motivovaných činov, ako aj v náraste emigrácie francúzskych židov do Izraela. Zameriava sa na tri hlavné znaky a to je v prvom rade spojenie nového antisemitizmu s populáciou moslimských prisťahovalcov, v druhom rade zakrývanie antisemitizmu antisionizmom a nakoniec zmena ukotvenia nového antisemitizmu na politickom spektre. Súčasťou práce je štúdia tvorby Dieudonného M'bala M'bala, známeho francúzskeho komika, ktorý je často kritizovaný za antisemitské prejav a výroky. Na jeho umeleckej a politickej dráhe sa následne snažím ukázať prvky nového antisemitizmu, ktoré som si stanovila v prvej časti.Department of European StudiesKatedra evropských studiíFaculty of Social SciencesFakulta sociálních vě

Real-space analysis of branch point motion in architecturally complex polymers

By means of large-scale molecular dynamics simulations, we investigate branch point motion in pure branched polymers and in mixtures of stars and linear chains. We perform a purely geometrical density-based cluster analysis of the branch point trajectories and identify regions of strong localization (traps). Our results demonstrate that the branch point motion can be described as the motion over a network of traps at the time scales corresponding to the reptation regime. Residence times within the traps are broadly distributed, even extending to times much longer than the side-arm relaxation time. The distributions of distances between consecutively visited traps are very similar for all the investigated branched polymers, even though tube dilation is much stronger in the star/linear mixtures than in the pure branched systems. Our analysis suggests that the diffusivity of the branch point introduced by hierarchical models must be understood as a parameter to account for the effective friction associated with the relaxed side arm, more than the description of a hopping process with a precise time scale.We acknowledge support from projects FP7-PEOPLE-2007-1-1-ITN (DYNACOP, EU), MAT2012-31088 (Spain), and IT654-13 (GV, Spain). We acknowledge the programs PRACE, HPC-Europa2 and ESMI (EU), and ICTS (Spain) for generous allocation of CPU time at GENCI (France), HLRS and FZJ-JSC (Germany), and CESGA (Spain).Peer Reviewe

Linear semiflexible polyelectrolytes in solutions

Title: Linear semiflexible polyelectrolytes in solutions Author: Petra Bačová Department: Faculty of Science, Charles University in Prague Supervisor: Doc. Ing. Zuzana Limpouchová, CSc. Supervisor's e-mail address: [email protected] Consultant: Mgr. Peter Košovan, PhD. Abstract: In this thesis I used the Molecular dynamics simulations for study of charged polymers (polyelectrolytes) and their behaviour in solutions. Wide range of polyelectrolytes are se- miflexible and in contrast to neutral polymers it is possible to influence their stiffness by changing the properties of solution as for example ionic strength. The chain flexibility may be characterized by the persistence length. Thesis explains how to express the persistence length from orientational correlation function which shows the double exponential decay. Two contributions to chain stiffness are discussed and the interest is concentrated around electrostatic persistence length which seems to be scale dependent. An effect of added salt on the chain conformation is studied. Salt is treated implicitly within the Debye-Hückel approximation. The results are confronted with OSF theory and the conclusions of vari- ational calculations of Maghi and Netz. The presented thesis describes the conformational behaviour of polyelectrolytes in salty solutions,..

Linear semiflexible polyelectrolytes in solutions

Title: Linear semiflexible polyelectrolytes in solutions Author: Petra Bačová Department: Faculty of Science, Charles University in Prague Supervisor: Doc. Ing. Zuzana Limpouchová, CSc. Supervisor's e-mail address: [email protected] Consultant: Mgr. Peter Košovan, PhD. Abstract: In this thesis I used the Molecular dynamics simulations for study of charged polymers (polyelectrolytes) and their behaviour in solutions. Wide range of polyelectrolytes are se- miflexible and in contrast to neutral polymers it is possible to influence their stiffness by changing the properties of solution as for example ionic strength. The chain flexibility may be characterized by the persistence length. Thesis explains how to express the persistence length from orientational correlation function which shows the double exponential decay. Two contributions to chain stiffness are discussed and the interest is concentrated around electrostatic persistence length which seems to be scale dependent. An effect of added salt on the chain conformation is studied. Salt is treated implicitly within the Debye-Hückel approximation. The results are confronted with OSF theory and the conclusions of vari- ational calculations of Maghi and Netz. The presented thesis describes the conformational behaviour of polyelectrolytes in salty solutions,..

Dieudonné as an example of new antisemitism in France

This bachelor thesis is aimed at specific character of the new anti-Semitism in France and concrete elements that differ the new wave from the old one. This topic is very up to date in today's France because of significant increase of anti-Semitic crimes and growing numbres of jews emigrating to Israel. Three main differences which I explore in my thesis are : connection between new anti-Semitism and moslim immigrants, overlapping anti-Semitism with anti-Zionism and shift of anti-Semitism on the political spetrum. Second part of my thesis is study of artistic production of Dieudonné M'bala M'bala, french entertainer known for his controversial statements. In his political and artistic career I am trying to find aspects of new anti-Semitism mentioned in the first part

Studium perzistenční délky lineárních polyelektrolytů v roztocích

Department of Physical and Macromolecular ChemistryKatedra fyzikální a makromol. chemieFaculty of SciencePřírodovědecká fakult