Download or read book Molecular Ordering Structure and Dynamics of Conjugated Polymers at Interfaces Multiscale Molecular Dynamics Simulations written by Yeneneh Yalew Yimer and published by . This book was released on 2014 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer-based solar cells (PSCs) require significant improvements in efficiency and life time in order to be commercially viable. Interfacial structure and morphology dictate the performance of PSCs, and these properties in turn depend on processing conditions and surface chemistry. To optimize device performance, detailed knowledge of the factors most critical to the molecular-level structure, morphology and dynamics of donor/acceptor systems at interfaces will be necessary. For one promising donor, poly(3-hexylthiophene (P3HT), we have utilized all-atom and coarse-grained molecular dynamics simulations to investigate such properties at liquid/vacuum, solid/liquid and solid/solid interfaces. At liquid/vacuum interfaces, static and dynamic properties of P3HT films and their dependence on temperature and molecular weight were studied. P3HT chains showed ordering through preferential exposure of side-chain at the interface, and surface tension showed strong dependence on temperature and molecular weight. Properties such as self-diffusion coefficients, chain end-to-end distance and torsion autocorrelations were also utilized to quantify the dynamics of the P3HT chains in the film. Both static and dynamic properties of P3HT were found to be in agreement with well-known models for polymers.Subsequent simulations of P3HT/water systems offered insight into the wetting behavior of P3HT and the nature of the solid-liquid interface in crystalline and amorphous P3HT. From contact angle calculations, different P3HT surfaces were determined to be hydrophobic. In the time scale of our simulations, no observable change in the orientation of the P3HT at interfaces was observed.Furthermore, the molecular ordering of P3HT close to substrates is expected to be the key to device performance. Ordering of P3HT chains at the interface can be tuned by altering the substrate surface chemistry. We investigated the effect of surface chemistry on the ordering of P3HT on self-assembled monolayers (SAMs) of n-alkanethiols. The results showed that the ordering of P3HT strongly depends on the P3HT-SAM interactions. The effect of solvent on the P3HT-SAM interactions was also studied. In addition, we characterized the surface properties of pure SAMs on gold 111. The end-functionalized network structure was found to be correlated to the adsorption sites. For P3HT/acceptor systems, all-atom simulations are challenging because of the need to access large spatial and temporal regimes. To overcome this, we developed a coarse-grained model for P3HT based on the all-atom force field. The coarse-grained model showed good agreement with bulk and interfacial properties obtained from the all-atom model and has a great potential for analyzing morphology and dynamics of P3HT/acceptor blends.
Download or read book Molecular Dynamics Simulations of Polymers and Micelles at Interfaces written by Nikolai Severin and published by . This book was released on 1999 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Computational Study of Structure and Dynamics of Bulk Conjugated Polymer Systems written by Kiran H. Kanekal and published by . This book was released on 2016 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conjugated polymers are a highly relevant class of materials due to their low processing cost and applicability in flexible electronic devices. A significant challenge in the field remains to relate the chemical structure of these materials with their morphology and dynamics, which in turn affect their charge transport characteristics. There are several experimental and computational methods that are commonly used when characterizing conjugated polymers. In this work, we attempt to synergistically apply these techniques so as to obtain a clear understanding of the properties that affect the structure and dynamics of conjugated polymers. A large experimental data set is used to validate molecular dynamics (MD) simulations of poly(3-hexylthiophene), a model conjugated polymer system. A sensitivity analysis of system and simulation parameters is performed, and the key factors affecting the conjugated polymer dynamics and configuration are found to be molecular weight, crystallinity, equilibration method, and force field parameters. Specifically, the atomistic partial charges are found to have the greatest influence on both properties. The identification of these key parameters will inform further studies of more complex conjugated polymer systems, elucidating the relationship between conjugated polymer chemistry and performance.
Download or read book Molecular Conformation and Dynamics of Conjugated Polymers Using Neutron and X ray Scattering and Simulations written by Caitlyn M. Wolf and published by . This book was released on 2020 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conjugated polymers (CPs) are advantageous materials for lower-cost and flexible organic electronic devices, such as organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), bioelectronics, chemical sensors, flexible displays, and wearable electronics. Their pi-conjugated backbones enable charge transport along the chain or through the pi-orbital overlap of neighboring chains. The molecular dynamics and morphology in the crystalline and amorphous phases of both pure and blended CPs have a direct impact on these mechanisms and therefore, the macroscopic performance of the material. A thorough understanding of this relationship is important for the future development of improved materials and devices. In this work, we utilize neutron and X-ray scattering together with molecular dynamics (MD) simulations and density functional theory (DFT) for a powerful combined experimental and theoretical approach to probing the structure and dynamics in poly(3-hexylthiophene) (P3HT) and other polythiophenes. We first utilize quasi-elastic neutron scattering (QENS) to perform a critical assessment of MD simulation force fields for P3HT. Although these models capture system-level dynamics well, they fail to accurately represent characteristic motions along the polymer backbone which play a critical role in charge transport processes. Next, we utilize density functional theory (DFT) to explore the non-bonded, intermolecular interactions of P3HT and use MD simulations to understand their influence on in-silico dynamics. With selective deuteration, characteristic relaxation times are extracted from QENS data for a set of P3HT polymers and oligomers to probe the effect of molecular weight and crystallinity on backbone and side-chain dynamics. Pure CPs are still susceptible to limited environmental stability and low mechanical durability (e.g. cracking), but blending CPs with a commodity polymer, e.g. polystyrene, can improve the lifetime and mechanical robustness of these materials while maintaining electronic performance at low amounts of the conjugated material. In our final study, small-angle neutron scattering (SANS) and wide-angle X-ray scattering (WAXS) are used to characterize phase separation and self-assembly in these polythiophene-polystyrene blends, and correlate phase morphology with macroscopic conductivity.
Download or read book Atomistic Computer Simulations of the Molecular Structure Thermodynamics and Dynamics of Glassy Polymers at Interfaces written by Kevin Francis Mansfield and published by . This book was released on 1991 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monte Carlo and Molecular Dynamics Simulations in Polymer Science written by Kurt Binder and published by Oxford University Press, USA. This book was released on 1995 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Talks about various computer simulation techniques used for macromolecular materials. This book describes how to use simulation to explain experimental data and gain insight into structure and dynamic properties of polymeric structures. Explanations are given on how to overcome challenges posed by large size and slow relaxation polymer coils.
Download or read book The Dynamics of Polymers at Interfaces written by Rebecca Ellen Taylor and published by . This book was released on 1995 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multiscale Modeling of Structure property Relationships in Polymers with Heterogenous Structure written by Yiyang Li and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The exceptional mechanical properties of polymers with heterogeneous structure, such as the high toughness of polyethylene and the excellent blast-protection capability of polyurea, are strongly related to their morphology and nanoscale structure. Different polymer microstructures, such as semicrystalline morphology and segregated nanophases, lead to coordinated molecular motions during deformation in order to preserve compatibility between the different material phases. To study molecular relaxation in polyethylene, a coarse-grained model of polyethylene was calibrated to match the local structural variable distributions sampled from supercooled atomistic melts. The coarse-grained model accurately reproduces structural properties, e.g., the local structure of both the amorphous and crystalline phases, and thermal properties, e.g., glass transition and melt temperatures, and dynamic properties: including the vastly different relaxation time scales of the amorphous and crystalline phases. A hybrid Monte Carlo routine was developed to generate realistic semicrystalline configurations of polyethylene. The generated systems accurately predict the activation energy of the alpha relaxation process within the crystalline phase. Furthermore, the models show that connectivity to long chain segments in the amorphous phase increases the energy barrier for chain slip within crystalline phase. This prediction can guide the development of tougher semicrystalline polymers by providing a fundamental understanding of how nanoscale morphology contributes to chain mobility. In a different study, the macroscopic shock response of polyurea, a phase segregated copolymer, was analyzed using density functional theory (DFT) molecular dynamics (MD) simulations and classical MD simulations. The two models predict the shock response consistently up to shock pressures of 15 GPa, beyond which the DFT-based simulations predict a softer response. From the DFT simulations, an analysis of bond scission was performed as a first step in developing a more fundamental understanding of how shock induced material transformations effect the shock response and pressure dependent strength of polyurea subjected to extreme shocks.
Download or read book Predicting Molecular Properties and Phase Behaviors for Conjugated Polymers written by Wenlin Zhang and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Conjugated polymers, though still outperformed by their inorganic counterparts, are promising materials for flexible electronics, including field-effect transistors and solar cells. The mechanical and electrical properties of this class of materials depend strongly on the morphological order. In order to design new materials and optimize existing polymers, establishing concrete links between fundamental molecular properties and structural order is necessary. As consequence, the ability to predict the properties of novel materials from their molecular structures is essential.This dissertation focuses on predicting fundamental properties and phase be- haviors of conjugated polymers from molecular structures. We develop tools and methods, combining molecular simulations and analytical theories, to predict ma- terial parameters, including the chain stiffness, the nematic coupling constant, and the Flory-Huggins parameter, for conjugated polymers. These fundamental parameters govern the mesoscale structures and phase behaviors for chains in melts and solutions, in turn affect the mechanical and electrical properties of conjugated polymers in the final semi-crystalline state.Using molecular dynamics (MD) simulations, we also investigate the role of thermal fluctuations in the performance of crystalline conjugated polymers. We show that thermal fluctuations can lead to cumulative lattice disorder in conjugated polymers, in turn enhance the inter-chain charge transport. Because the fluctuations of crystal shape are related to the mechanical properties of conjugated polymers, we can also obtain the elastic moduli for crystalline conjugated polymers by measuring the fluctuating box sizes in MD simulations.Altogether, this dissertation reports our progress on predicting the electrical and mechanical properties from molecular structures for conjugated polymers in both the precursor (melt and solution) and the crystalline states. Our results lay the foundation for understanding the structure-property relations of conjugated polymers in their final semicrystalline forms.
Download or read book Molecular Simulation Methods for Predicting Polymer Properties written by Vassilios Galiatsatos and published by John Wiley & Sons. This book was released on 2005-02-03 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the thousands of synthesized polymers, new polymeric substances and materials with new, often unusual, properties often arise. Consequently, this presents a problem in determining the physical properties of polymers, and thus makes it difficult to ascertain how to synthesize polymers with desired properties. This book discusses what molecular modelling can do to predict the properties of realistic polymer systems. Organized by property, each chapter will address the methods one may use to study the particular system. * Focuses on polymer properties rather than methods, making it more accessible to the average scientist/engineer * All important polymers will be covered, such as amorphous polymers, semicrystalline polymers, elastomers, emulsions, polymer interfaces and surfaces * Chapters contributed by experts in the field * Discusses current commercial software used in molecular simulation
Download or read book Molecular Dynamics Studies of Polymers in Solution and at Interfaces written by Hong Liu and published by . This book was released on 2000 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Dynamics Simulations of Amphiphilic Macromolecules at Interfaces written by Selina Nawaz and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this thesis is to investigate the structural and thermodynamic properties of biologically and technological relevant macromolecules when placed at soft interfaces. In particular two amphiphilic macromolecules characterized by different topologies have been investigated namely amphiphilic dendrimers and linear block copolymers. This goal is achieved using a multiscale approach which includes all-atom, united atom and coarse grained models by means of molecular dynamic simulations. Amphiphilic dendrimers have shown to be promising building blocks for a range of interfacial materials and can be used in applications such as surface-base sensors or surface nanopatterning. In this part of the thesis by means of all-atom molecular dynamics simulations, we investigated the structure and stability of alkyl-modified polyamido-amide (PAMAM) dendrimers at the air/water interface as a function of the number and the relative position of the modified end groups. We found that the PAMAM dendrimer with all terminal groups functionalized is more stable at the interface than the Janus dendrimer, where only half the amine groups are modified. These results indicate that monolayers of fully functionalized molecules could be as stable as (or more stable than) those self-assembled from Janus molecules. The second part of the thesis is devoted to model a particular family of amphiphilic triblock copolymer sold as Pluronics, consisting of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) arranged as PEO-PPO-PEO. There is evidence that this class of amphiphilic materials can be used for different biological applications. A fuller understanding of the molecular mechanisms underpinning their interactions with living cells is essential for ensuring the polymers safety and efficacy in biomedical applications. Using united-atom molecular dynamics simulations and membrane lysis assays, we investigated the relationship between the molecular conformations of a subset of the Pluronic copolymers (L31, L61, L62 and L64) and their haemolytic activity. Our computational studies suggest that the hydrophilic blocks in these copolymers interact with the polar head groups of lipid molecules, resulting in a predicted modification of the structure of the membranes. Parallel membrane lysis assays in human erythrocytes indicate differences in the rates of haemolysis, as a result of incubation with these polymers, which correlate well with the predicted interactions from the atomistic simulations. The computational data thus provide a putative mechanism to rationalize the available experimental data on membrane lysis by these copolymers. The data quantitatively agree with haemoglobin release endpoints measured when copolymers with the same molecular weight and structure as of those modelled are incubated with erythrocytes. The data further suggest some new structure- function relationships at the nanoscale that are likely to be of importance in determining the biological activity of these otherwise inert copolymers. In order to visualise the effect of Pluronics at a length and time scale closer to the experimental one, in the third part of the thesis we developed a coarse-grained model for the amphiphilic copolymers within the framework of the MARTINI forcefield (Marrink et al., J. Phys. Chem. B, 2007, 111, 7812). The MARTINI force field is usually parameterized targeting thermodynamic properties. In addition to this, we further parameterized it based on atomistic simulations validating the parameters against structural properties of the copolymers. The ability of the model to predict several structural and thermodynamic properties of the atomistic system have been explored. The aim of this work is to be able to simulate the polymer/lipid interface at polymer concentration similar to the experimental one.
Download or read book Molecular Dynamics Simulations of Polymers written by Jie Han and published by . This book was released on 1995 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theoretical Study on Excited state Molecular Dynamics of Conjugated Polymers and Nonvanishing First Hyperpolarizabilities of Centrosymmetric Molecules written by 張耀文 and published by . This book was released on 2008 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Conjugated Polymers written by John R. Reynolds and published by CRC Press. This book was released on 2019-03-27 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Fourth Edition of the Handbook of Conducting Polymers, Two-Volume Set continues to be the definitive resource on the topic of conducting polymers. Completely updated with an extensive list of authors that draws on past and new contributors, the book takes into account the significant developments both in fundamental understanding and applications since publication of the previous edition. One of two volumes comprising the comprehensive Handbook, Conjugated Polymers: Perspective, Theory, and New Materials features new chapters on the fundamental theory and new materials involved in conducting polymers. It discusses the history of physics and chemistry of these materials and the theory behind them. Finally, it details polymer and materials chemistry including such topics as conjugated block copolymers, metal-containing conjugated polymers, and continuous flow processing. Aimed at researchers, advanced students, and industry professionals working in materials science and engineering, this book covers fundamentals, recent progress, and new materials involved in conducting polymers and includes a wide-ranging listing of comprehensive chapters authored by an international team of experts.
Download or read book Multiscale Modelling of Organic and Hybrid Photovoltaics written by David Beljonne and published by Springer. This book was released on 2014-08-12 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry presents critical reviews of the present and future trends in modern chemical research. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field. Review articles for the individual volumes are invited by the volume editors. Readership: research chemists at universities or in industry, graduate students.
Download or read book Visualizing Chemistry written by National Research Council and published by National Academies Press. This book was released on 2006-06-01 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scientists and engineers have long relied on the power of imaging techniques to help see objects invisible to the naked eye, and thus, to advance scientific knowledge. These experts are constantly pushing the limits of technology in pursuit of chemical imagingâ€"the ability to visualize molecular structures and chemical composition in time and space as actual events unfoldâ€"from the smallest dimension of a biological system to the widest expanse of a distant galaxy. Chemical imaging has a variety of applications for almost every facet of our daily lives, ranging from medical diagnosis and treatment to the study and design of material properties in new products. In addition to highlighting advances in chemical imaging that could have the greatest impact on critical problems in science and technology, Visualizing Chemistry reviews the current state of chemical imaging technology, identifies promising future developments and their applications, and suggests a research and educational agenda to enable breakthrough improvements.
