Molecular Insight into the Effects of Clustering on the Dynamics of Ionomers in Solutions

SS Mohottalalage and C Kosgallana and M Senanayake and S Wijesinghe and NC Osti and D Perahia, ACS MACRO LETTERS, 12, 1118-1124 (2023).

DOI: 10.1021/acsmacrolett.3c00353

Ionizable groups tethered to polymersenable their many currentand potential applications. However, these functionalities drive theformation of physical networks through clustering of the ionic groups,resulting in constrained dynamics of the macromolecules. Understandingthe molecular origin of this hindrance remains a critical fundamentalquestion, whose solution will directly impact the processing of ionizablepolymers from molecules to viable materials. Here, using quasielasticneutron scattering accompanied by molecular dynamics simulations,segmental dynamics of slightly sulfonated polystyrene is studied insolutions as the cohesion of the ionic assemblies is tuned. We findthat in cyclohexane the ionic assemblies act as centers of confinement,affecting dynamics both on macroscopic lengths and in the vicinityof the ionic assemblies. Addition of a small amount of ethanol affectsthe packing of the ionizable groups within the assemblies, which inturn enhances the chain dynamics.

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