Unraveling the dynamics of aminopolymer/silica composites

The structure and dynamics of a model branched polymer, representing poly(ethylenimine), was investigated through coarse-grained molecular dynamics simulations and neutron scattering experiments. The monomer concentration and solvent quality were varied in the simulations and detailed comparisons between the calculated structural and dynamical properties of the unconfined polymer and those confined within an adsorbing and non-adsorbing cylindrical pore, representing the silica based structural support of the composite, were made. The simulations show a direct relationship in the structure of the polymer and the non-monotonic dynamics of the polymers as a function of monomer concentration within an adsorbing cylindrical pore. However, the non-monotonic behavior disappears for the case of the branched polymer within a non-adsorbing cylindrical pore. Overall the simulation results are in good agreement with quasi-elastic neutron scattering (QENS) studies of branched poly(ethylenimine) in mesoporous silica (SBA-15) of comparable size, suggesting an approach that can be a useful guide for understanding how to tune porous polymer composites for enhancing desired dynamical and structural behavior targeting carbon dioxide adsorption.