Physical property scaling relationships for polyelectrolyte complex micelles*

Polyelectrolyte complex micelles (PCMs) are widely used in the delivery of hydrophilic payloads. As oppositely charged polyelectrolytes assemble, counterions are liberated, however, when counterion concentrations are sufficiently high they prevent, or disrupt, polyelectrolyte complexation. Measuring complex stability versus salt provides a metric for the strength of ion pairing between polymers. PCM attributes are also strongly dependent on the size and chemical structure of each polymer block. Neutral blocks drive nanoscale phase separation while charged blocks control micelle core size and stability. An understanding of physical property behavior controlled by block size, chemistry, and salt conditions is crucial when designing for use in dynamic or biological environments and provide a greater understanding of the physics of polyelectrolyte assembly. In this work, we use small angle x-ray scattering, light scattering, and electron microscopy to determine scaling behaviors of micelle shape, size, and stability for many commonly used polyelectrolytes.