A Combined Density Functional and Monte Carlo Study of Polycarbonate
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A Combined Density Functional and Monte Carlo Study of Polycarbonate R. O. Jones and P. Ballone[*] Institut f¨ur Festk¨orperforschung, Forschungszentrum J¨ulich, D-52425 J¨ulich, Germany ABSTRACT Density functional computations have been performed to investigate the structure, potential energy surface and reactivity for organic systems closely related to bisphenol-A-polycarbonate(BPAPC). The results provide the basis for the construction of two different empirical models, the first extending the atomistic simulations into the mesoscopic range ( atoms and s), the second providing an idealized description of polymerization in BPA-PC. The combination of models and computational techniques focusing on different length and time scales provides a route to determine mechanical and thermal properties of materials without experimental input.
INTRODUCTION Polymer science was one of the first fields where the importance of multi-scale relations and phenomena was recognized, providing the motivation for renormalization group approaches [1]. Standard applications of these methods to polymers assume that their behavior arises from the cooperative interaction of different length and time scales, while the details of the atomic and chemical structure determine some collective parameters, but are otherwise unimportant. The vast literature on these methods testifies to their power and success. Nevertheless, we are increasingly confronted with problems that require a detailed description of the structure, dynamics and chemical properties on different scales of time and length, so that we can investigate all those properties that are not universal. We shall show here that different models and computational methods can be combined to provide a detailed description of polymers, using bisphenol A polycarbonate (BPAPC) as an example. The polycarbonate family includes materials with outstanding mechanical, optical and thermal properties, and a wide range of applications. Although production and processing of polycarbonates have been carried out on an industrial scale for several decades, there remain important questions concerning the relation between the macroscopic behavior and the structure and chemistry at the atomistic level that require a multi-approach investigation. A detailed understanding of the relationship between structure and properties should provide the basis for the development of new variants of these materials. Our strategy has been to study the atomistic behavior by parameter-free density functional (DF) calculations, which provide the basis for developing empirical models that extend the size atoms and s). This allows the and time scales into the mesoscopic domain ( investigation of inhomogeneous systems, and of mechanical and thermal properties. Moreover, the DF results provide both the inspiration and the input parameters for more idealized models, with which we have studied the equilibrium polymerization of polycarbonates.
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