Conjugated polymers are investigated extensively as semiconducting materials as an alternative to their inorganic materials. Their properties and hence their performance is strongly dependent on their morphology. It is critical to understand the physical laws governing their behavior and establish relationships between molecular structure and material property. In this dissertation, we attempt to predict material properties like nematic coupling constant and phase behavior of polymer mixtures. We combine molecular dynamics simulations with developed tools to explore material properties. We use molecular dynamics simulations with self-consistent field theory (SCFT) to determine the nematic coupling constant [alpha]. In other studies, we combine molecular dynamics simulations with thermodynamic integration along well-defined paths to determine Flory Huggins interaction parameter [chi]. We improve upon our methods to overcome limitations related to the previously developed methods. The newly developed simulation methods are validated and used to explore the effect of different factors on material properties. This dissertation is our progress in predicting structure-property relationships for polymers and developing new tools to aid in this direction. These efforts help us in predicting the mechanical and electrical properties of conjugated polymers from their molecular properties.

Mathematical Physics in Theoretical Chemistry deals with important topics in theoretical and computational chemistry. Topics covered include density functional theory, computational methods in biological chemistry, and Hartree-Fock methods. As the second volume in the Developments in Physical & Theoretical Chemistry series, this volume further highlights the major advances and developments in research, also serving as a basis for advanced study. With a multidisciplinary and encompassing structure guided by a highly experienced editor, the series is designed to enable researchers in both academia and industry stay abreast of developments in physical and theoretical chemistry. Brings together the most important aspects and recent advances in theoretical and computational chemistry Covers computational methods for small molecules, density-functional methods, and computational chemistry on personal and quantum computers Presents cutting-edge developments in theoretical and computational chemistry that are applicable to graduate students and research professionals in chemistry, physics, materials science and biochemistry

Much of chemistry, molecular biology, and drug design, are centered around the relationships between chemical structure and measured properties of compounds and polymers, such as viscosity, acidity, solubility, toxicity, enzyme binding, and membrane penetration. For any set of compounds, these relationships are by necessity complicated, particularly when the properties are of biological nature. To investigate and utilize such complicated relationships, henceforth abbreviated SAR for structure-activity relationships, and QSAR for quantitative SAR, we need a description of the variation in chemical structure of relevant compounds and biological targets, good measures of the biological properties, and, of course, an ability to synthesize compounds of interest. In addition, we need reasonable ways to construct and express the relationships, i. e. , mathematical or other models, as well as ways to select the compounds to be investigated so that the resulting QSAR indeed is informative and useful for the stated purposes. In the present context, these purposes typically are the conceptual understanding of the SAR, and the ability to propose new compounds with improved property profiles. Here we discuss the two latter parts of the SARlQSAR problem, i. e. , reasonable ways to model the relationships, and how to select compounds to make the models as "good" as possible. The second is often called the problem of statistical experimental design, which in the present context we call statistical molecular design, SMD. 1.

Improved knowledge connecting the chemistry, structure, and properties of polymers is necessary to develop advanced materials in a materials-by-design approach. Molecular dynamics (MD) simulations can provide tremendous insight into how the fine details of chemistry, molecular architecture, and microstructure affect many physical properties; however, they face well-known restrictions in their applicable temporal and spatial scales. These limitations have motivated the development of computationally-efficient, coarse-grained methods to investigate how microstructural details affect thermophysical properties. In this dissertation, I summarize my research work in structure-based coarse-graining methods to establish the link between molecular-scale structure and macroscopic properties of two different polymers. Systematically coarse-grained models were developed to study the viscoelastic stress response of polyurea, a copolymer that segregates into rigid and viscous phases, at time scales characteristic of blast and impact loading. With the application of appropriate scaling parameters, the coarse-grained models can predict viscoelastic properties with a speed up of 5-6 orders of magnitude relative to the atomistic MD models. Coarse-grained models of polyethylene were also created to investigate the thermomechanical material response under shock loading. As structure-based coarse-grained methods are generally not transferable to states different from which they were calibrated at, their applicability for modeling non-equilibrium processes such as shock and impact is highly limited. To address this problem, a new model is developed that incorporates many-body interactions and is calibrated across a range of different thermodynamic states using a least square minimization scheme. The new model is validated by comparing shock Hugoniot properties with atomistic and experimental data for polyethylene. Lastly, a high fidelity coarse-grained model of polyethylene was constructed that reproduces the joint-probability distributions of structural variables such as the distributions of bond lengths and bond angles between sequential coarse-grained sites along polymer chains. This new model accurately represents the structure of both the amorphous and crystal phases of polyethylene and enabling investigation of how polymer processing such as cold-drawing and bulk crystallization affect material structure at significantly larger time and length scales than traditional molecular simulations.

This book offers readers a snapshot of the progression of molecular modeling in the electronics industry and how molecular modeling is currently being used to understand materials to solve relevant issues in this field. The reader is introduced to the evolving role of molecular modeling, especially seen from the perspective of the IEEE community and modeling in electronics. This book also covers the aspects of molecular modeling needed to understand the relationship between structures and mechanical performance of materials. The authors also discuss the transitional topic of multiscale modeling and recent developments on the atomistic scale and current attempts to reach the submicron scale, as well as the role that quantum mechanics can play in performance prediction.

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

This book discusses the fundamentals of molecular simulation, starting with the basics of statistical mechanics and providing introductions to Monte Carlo and molecular dynamics simulation techniques. It also offers an overview of force-field models for molecular simulations and their parameterization, with a discussion of specific aspects. The book then summarizes the available know-how for analyzing molecular simulation outputs to derive information on thermophysical and structural properties. Both the force-field modeling and the analysis of simulation outputs are illustrated by various examples. Simulation studies on recently introduced HFO compounds as working fluids for different technical applications demonstrate the value of molecular simulations in providing predictions for poorly understood compounds and gaining a molecular-level understanding of their properties. This book will prove a valuable resource to researchers and students alike.