We probe the role of charge density as a determinant of dynamics in polyelectrolyte complexes and coacervates through investigation of two model systems. First, we compare the phase behavior and rearrangement dynamics of complexes of two types of polycationic micelles with poly(styrene sulfonate). Dynamic light scattering reveals that complexes formed from micelles with poly(dimethylamino ethyl methacrylate-stat-oligo(ethylene glycol) methyl ether methacrylate) P(DMAEMA-stat-OEGMA) coronas rearrange much more quickly in the presence of excess polyanion than do complexes formed from micelles with PDMAEMA coronas in which the charge density is not diluted by incorporation of neutral, hydrophilic OEGMA units. In conjunction with molecular dynamics simulations on model polymer brushes, we conclude that decreasing the charge density decreases the energy barrier to rearrangement, resulting in faster rearrangement kinetics. We hypothesize that in complex coacervates, these faster rearrangement kinetics should be reflected in a shift to higher crossover frequencies in small-amplitude oscillatory shear measurements. We test this hypothesis by investigating a second model system, coacervates of P(DMAEMA-stat-OEGMA) and poly(acrylic acid), as a function of charge fraction and oligo(ethylene glycol) chain length. Our results bring new insight into charge density’s central role in determining the dynamics of association and rearrangement in polyelectrolyte complexes and coacervates, and its use as a method for controlling the materials properties of these systems.

Charge density as a determinant of dynamics in polyelectrolyte complexes and coacervates

254th National Meeting (2017)

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