(584h) Prediction of Renewable Polymer Properties Using Quantum and Molecular Modeling

An important trend in the development of new polymeric materials has been a movement toward polymers that are derived from renewable resources. Polylactide (PLA) and a family of polyhydroxyalkanoates (PHAs) have received widespread attention due to their physical properties, ease of synthesis, and formation from low cost agricultural products. Presently, the cost of manufacturing many of these polymers is sufficiently low that their use as commodity polymers is economically viable. Individually many of these polymers are lacking in some physical property, but blends of these materials have been shown to yield the desirable properties. Synthesis and testing of all possible copolymers and polymer blends required for a diverse range of applications would be prohibitively time consuming and expensive. Therefore, a promising alternative is to use molecular modeling to predict the physical and transport properties of these polymer systems.

The Groningen Machine for Chemical Simulations (GROMACS) is a molecular simulation engine designed to take advantage of message-passing, parallel-processing, computer architectures so that large chemical systems can be easily modeled by molecular dynamics (MD) and replica exchange MD techniques. Simulations of polymer properties, including heat capacity, rheological behavior, and small molecule diffusion characteristics, have been conducted using equilibrium and nonequilibrium MD methods. These simulations were conducted using a variant of the OPLS force field, where the force field parameters were optimized specifically for these polymer systems using results from diffraction experiments and extensive density functional theory (DFT) simulations of the respective oligomer systems. Further, the quantum mechanical simulations yielded vital information about the degradation behavior of these polymer systems. The results from all of these simulations provide key insights into structure property relationships for these bioinspired polymer systems.