Mechanistic modeling of nitroxide-mediated controlled radical polymerization

In recent years, there has been significant interest in polymeric materials possessing novel architectures. In particular, the macroscopic properties of copolymeric materials are greatly affected by the arrangement of monomers along the chain. It is possible for copolymers to possess the same size and overall composition, but the topology of the monomer sequencing is of key interest as it dictates the macroscopic physical properties of these materials. With the analysis of these materials as the ultimate goal, mechanistic modeling studies were conducted for styrene and 4-acetoxystyrene homopolymerization and their copolymerization.;Initial models involved the use of continuum-based modeling utilizing the method of moments. These models were advantageous as they provided a high level of detail of the polymerization system while maintaining a reasonable model size with limited computational time. Initial modeling work focused on the nitroxide-mediated controlled radical polymerization (NM-CRP) of styrene. Using available parameters from the literature, the model was fit to experimental molecular weight data and provided results that were consistent with experimental results from the literature. This methodology was next utilized to model the thermal polymerization and NM-CRP of 4-acetoxystyrene. In these studies a combined experimental and modeling approach was used to determine key rate parameters for 4-acetoxystyrene which have not been presented in the literature to date. The propagation rate coefficient was determined experimentally by collaborators with the use of pulsed laser polymerization (PLP) while rate parameters for thermal initiation, termination, and nitroxide uncapping were determined using model fits.;Stochastic models based on kinetic Monte Carlo (KMC) were developed to provide a more detailed view of copolymerization with emphasis on gradient copolymers. Initial KMC models focused on the generation of the copolymer chemical composition distribution (CCD) which captures overall compositions for individual chains in the system. This methodology was expanded to track the full sequence of each chain and allowed for the generation of triad and sequence length distributions. This powerful methodology allows for a complete description of copolymerization systems which can be used to assess sequence statistics and design copolymer architecture.