Averaging effects in PGSE NMR attenuations observed in bimodal molecular weight PMMA solutions

NMR diffusion measurements have proven to be a very powerful technique for probing the solution dynamics of polymer systems. In theory, it is possible to extract a range of useful information including molecular weights from the diffusion data. In practice, especially outside the infinite dilution regime, the data analysis is further complicated by numerous effects including macroscopic and microscopic averaging. Here the averaging effects in dilute bimodal narrow molecular weight poly(methyl methacrylate) in deuterated chloroform solutions are studied at 298 K and cogent models developed to analyze the data. Simulations are performed which represent different limits of diffusive behavior in bimodal solutions and the suitability of the simulations are found to be dependent on the ratio of the molecular weights in the solution.