Abstract
The segmental dynamics of complex coacervates were investigated as a function of salt concentration and a charge type using quasi-elastic neutron scattering (QENS). The coacervates were prepared by mixing two oppositely charged polyether-based polyelectrolyte solutions functionalized for cationic ammonium and guanidinium groups or anionic sulfonate groups. For the QENS time scale, the intrinsic ion pairs were considered effective cross-links, and therefore the dynamics of chain segments between the intrinsic junctions were probed. We observed that as salt concentration increases, both the number of mobile chain segments and their segmental dynamics increase for ammonium-based coacervates where the electrostatic interaction primarily governs the phase behavior. However, the guanidinium-based coacervates show slow and nearly identical segmental relaxation independent of the salt concentration, which is potentially attributed to the non-electrostatic interactions. The combination of the chemical structure of ionic moieties, salt concentration, and temperature plays a significant role to determine polymer chain dynamics mainly affected by the strength of ionic bonding.
Published Version
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