Unraveling the Dynamics of Aminopolymer/Silica Composites

Abstract

The structure and dynamics of a model branched polymer was investigated through molecular dynamics simulations and neutron scattering experiments. The polymer confinement, 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 nonadsorbing 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 nonmonotonic dynamics as a function of monomer concentration within an adsorbing cylindrical pore. However, the nonmonotonic behavior disappears for the case of the branched polymer within a nonadsorbing 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.

Exploring the Acid Gas Sorption Properties of Oxidatively Degraded Supported Amine Sorbents

“…However this difference may also be due to a difference in topology between the two systems. [19,39] It is understood that PEI binds to SBA-15 through hydrogen-bonding interactions between silanol species and primary amines. [39] As there are no primary amines in MePEI, the hydrogen bonding interactions will be more limited.…”

“…[19,39] It is understood that PEI binds to SBA-15 through hydrogen-bonding interactions between silanol species and primary amines. [39] As there are no primary amines in MePEI, the hydrogen bonding interactions will be more limited. Also, methylating all the amines likely makes the system more hydrophobic than materials made with conventional PEI.…”

“…Recent SANS and theoretical work suggests that initially aminopolymers form strong interactions with the pore wall through primary amine groups, creating a monolayer along the pore walls. [19,39] After the monolayer formation, polymerpolymer interactions dominate as the polymer forms 'plugs' in the mesopores, similar to the bulk (non-encapsulated) polymer. [19,39] This helps rationalize why a greater decrease is observed in the MePEI-SBA, than PEI-SBA.…”

“…[19,39] After the monolayer formation, polymerpolymer interactions dominate as the polymer forms 'plugs' in the mesopores, similar to the bulk (non-encapsulated) polymer. [19,39] This helps rationalize why a greater decrease is observed in the MePEI-SBA, than PEI-SBA. As MePEI-SBA has no primary amines, the polymer-support interactions will be much weaker, leading to a greater amount of polymer mobility and possibly leaching.…”

Water dynamics in rigid ionomer networks

“…The inherently large difference in the scattering cross section between proton (H, σ = 80.26 b) and deuterium (D, σ = 2.05 b) makes QENS the technique of choice to study segmental dynamics of ionomers 38,39 as well as that of water in confinement. [40][41][42] Here, using QENS, we explore the effects of chain rigidity on the local dynamics in membranes that consist of substituted polyphenylene backbone with sulfonated ionic groups shown in Figure 1. We find that similar to other ionomers, water occupies multiple sites with a different degree of association and displays fast and slow dynamic modes; however, the distribution of the molecules is strongly affected by the bundle structure arising from the chain rigidity.…”