Macromolecular Theory and Simulations

Cover image for Vol. 23 Issue 7

Special Series: Modeling for Polymer Design

Guest-edited by Christopher Barner-Kowollik, this series publishes in an on-going fashion invited articles by leading researchers to document the rapid progress in this field.

 

Kinetic Modeling as a Tool to Understand and Improve the Nitroxide Mediated Polymerization of Styrene

design_20_4_1_Reyniers.jpgLien Bentein, Dagmar R. D'hooge, Marie-Françoise Reyniers,* Guy B. Marin

Detailed kinetic simulations, systematically accounting for diffusional limitations, for SG1 and TEMPO mediated bulk polymerization of styrene reveal the importance of transfer reactions on the polymer properties. Simulations indicate that careful control of the polymerization conditions can succeed in suppressing transfer reactions and allows obtaining an important improvement of average chain length, polydispersity index, and end-group functionality.

Macromol. Theory Simul. DOI: 10.1002/mats.201000081

 

Kinetic Simulations of Atom Transfer Radical Polymerization (ATRP) in Light of Chain Length Dependent Termination

design_19_7_1_Monteiro.jpgGeoffrey Johnston-Hall, Michael J. Monteiro*

Kinetic simulations using the composite kt model allows a better understanding of the effects of the persistent radical affecting ATRP or for that matter any activation-deactivation system. It also provides a better fit to experimental data in either bulk or solution conditions for ATRP polymerizations carried out at 110°C. The PRE controls the molecular weight distribution, exemplified by a linear increase in Mn with conversion and a low PDI.

Macromol. Theory Simul. DOI: 10.1002/mats.201000023

 

Describing the Structure of a Randomly Hyperbranched Polymer

design_19_5_n_Perrier.jpgDominik Konkolewicz, Angus Gray-Weale, Sébastien Perrier*

A model for the structures of hyperbranched polymers is outlined, focusing on how physical considerations affect the properties of the polymer. This model can predict the structures of a wide variety of randomly hyperbranched polymers, in each case the polymer is made by random attachment of the units. The predictions of the model can be compared to experiments to test whether an experimental polymer is consistent with the hyperbranched structures predicted by the model.

Macromol. Theory Simul. DOI: 10.1002/mats.201000006

 

Kinetic Simulations of Reversible Chain Transfer Catalyzed Polymerization (RTCP): Guidelines to Optimum Molecular Weight Control

design_19_1_n_Vana.jpgPhilipp Vana,* Atsushi Goto*

Compartmentalization and nitroxide partitioning in nitroxide-mediated radical polymerization in dispersed systems have been investigated by modeling and simulations. Compartmentalization comprises the segregation effect on termination and the confined space effect on deactivation. Under certain conditions, it is possible to obtain an improvement in both control and livingness.

Macromol. Theory Simul. DOI: 10.1002/mats.200900064

 

Nitroxide-Mediated Radical Polymerization in Dispersed Systems: Compartmentalization and Nitroxide Partitioning

design_19_1_n_Zetterlund.jpgPer B. Zetterlund

Compartmentalization and nitroxide partitioning in NMP in dispersed systems have been investigated by modeling and simulations. Compartmentalization comprises the segregation effect on termination and the confined space effect on deactivation. Under certain conditions, it is possible to obtain an improvement in both control and livingness. The particle size threshold for compartmentalization, decreases with any system change that leads to a decrease in the number of propagating radicals and/or nitroxides per particle, and vice versa. There is direct competition between the confined space effect on deactivation and nitroxide exit-the more water-soluble the nitroxide, the weaker the confined space effect. Nitroxide partitioning leads to an increase in polymerization rate and loss in control/livingness.

Macromol. Theory Simul. DOI: 10.1002/mats.200900051

 

Quantum-Chemical Modeling of Free-Radical Polymerization

design_18_7-8_2_Coote.jpgMichelle L. Coote

This article reviews recent progress in the application of quantum chemistry to radical polymerization processes, with a principle focus on establishing the current best-practice methodology for obtaining chemically accurate calculations. The scope and limitations of computational chemistry for this field are also discussed, and some of its leading applications in the areas of ab initio kinetic modeling and computer-aided reagent design are highlighted

Macromol. Theory Simul. DOI: 10.1002/mats.200900050

 

Optimum Reaction Conditions for the Synthesis of Macromonomers Via the High-Temperature Polymerization of Acrylates

design_18_7-8_nn_Barner-Kowollik.jpgThomas Junkers*, Christopher Barner-Kowollik*

Macromonomers are valuable synthetic building blocks: They can be copolymerized with low molecular weight monomers to generate brush-like structures or serve as conjugation substrates in pericylic, metathesis, and thiolene reactions. Based on earlier reports on the facile high temperature formation of macromonomers from acrylates, a complex kinetic model is developed which accounts for the key reactions constituting the macromonomer formation process. On the basis of the kinetic model, the important rate coefficients governing acrylate polymerization (e.g., -scission and termination rate coefficients of midchain radicals, backbiting and intramolecular chain transfer rate coefficients) as well as the reaction conditions (e.g., initial monomer concentration, reaction temperature, radical flux) are systematically varied and their influence on the synthetic success is critically evaluated. The systematic coefficient variation reveals that there exist optimum reaction conditions under which the high temperature macromonomers formation may be conducted with maximum success. The present study provides a concise summary of these conditions.

Macromol. Theory Simul. DOI: 10.1002/mats.200900025

 

Kinetic Modeling of Nitroxide-Mediated Polymerization: Conditions for Living and Controlled Polymerization

design_18_7-8_nn_Guillaneuf.jpgDidier Gigmes, Denis Bertin, Catherine Lefay, Yohann Guillaneuf*

Simulations of conversion versus time, molecular weight (Mn), polydispersity index (PDI), and living fractions versus conversion plots are performed using the PREDICI software, to study the influence of several kinetic parameters on the living and controlled character of nitroxide-mediated polymerization (NMP). In particular, the crucial role of the main equilibrium represented by both kd and kc (the rate coefficients respectively of dissociation and recombination) is highlighted. On the other hand, the importance of the initiation step, the targeted Mn value, and the initial excess of free nitroxide are also demonstrated. It is further proved that side reactions, such as disproportionation and transfer to solvent, have a strong impact on the polymerization characteristics.

Macromol. Theory Simul. DOI: 10.1002/mats.200900019

 

Special Article Series on 'Modeling for Polymer Design'

design_18_7-8_1_Barner-Kowollik.jpgChristopher Barner-Kowollik

As shown by a series of modeling studies, advanced synthetic polymer chemistry and the physical understanding of the underpinning reaction kinetics are inextricably linked. Both areas must be viewed as one unit if synthetic processes are to be optimized (or even made possible) with regard to the chosen reaction conditions as well as the addition and design of controlling agents and/or catalysts. The articles in the present series are designed to be used as a bridge between synthesis and modeling.

Guest-edited by Christopher Barner-Kowollik (University of Karlsruhe), the new article series "Modeling for Polymer Design" will highlight the most important developments and trends in this field.

Macromol. Theory Simul. DOI: 10.1002/mats.200900046

 

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