The influence of charge ratio on transient networks of polyelectrolyte complex micelles

Abstract

We study the influence of charge ratio on the transient network formation of bridged polyelectrolyte complex micelles. The polyelectrolyte complex micelles are based on mixing an ABA triblock copolymer in which the A-blocks are positively charged and the B-block is neutral and hydrophilic, and a negatively charged homopolymer. We investigate the microstructure of our samples with (dynamic) light scattering and small-angle X-ray scattering, and the mechanical properties by rheometry. At charge stoichiometric conditions, we obtain flowerlike polyelectrolyte complex micelles. These micelles become interconnected at high concentrations, leading to a sample-spanning transient network. For excess negative charge conditions, we obtain so-called ‘soluble complexes’ which are small aggregates carrying the excess negative charge on the polyelectrolyte complex parts. For excess positive charge conditions, micelles stay intact, because the triblock copolymers can localize the excess positive charge at the periphery of the micellar corona. This structural asymmetry is not reflected in the mechanical properties, which show a strong decrease in viscosity on either side of the charge stoichiometric point.