Effect of Charged Block Length Mismatch in Double Diblock Polyelectrolyte Complex Micelles*

When two oppositely charged hydrophilic block polyelectrolytes are mixed, they can spontaneously self-assemble into micelles with polyelectrolyte complex (PEC) cores and hydrophilic coronas. These polyelectrolyte complex micelles (PCMs) are responsive to salt, temperature and pH, which makes them attractive carriers for hydrophilic cargo in biological applications. It is commonly assumed that the charged block lengths of the constituent diblocks must be identical for assembly to occur. In our work, we explore the role of charged block length mismatch in PCMs through a series of model diblocks with a wide range of block asymmetries. We use a combination of small-angle x-ray scattering and dynamic light scattering to measure the core size and hydrodynamic radius of our PCMs, which allows us to connect molecular features to PCM structural characteristics. Our results provide guidelines for the development of asymmetric PEC assemblies both in PEC gels and PCMs.