Rheology of Block Polyelectrolyte Solutions and Gels: A Review

We review recent experimental results on the rheology of block polyelectrolyte solutions, focusing mainly on diblock and triblock architectures and the effects of block polyelectrolyte concentration, block composition, solution pH, and ionic strength. Micellar solutions of diblock polyelectrolytes are typically viscoelastic liquids at a low concentration; however, gel formation can occur at higher concentrations when micelle corona chains begin to interpenetrate or interact. The rheology can be tuned by varying pH or ionic strength or through the addition of hydrophobic groups along the corona chain. Triblock architectures form elastic gels, analogous to neutral telechelic associative polymers. However, the charged nature of the backbone promotes the formation of a highly networked structure, enabling gel formation at lower concentrations than those observed with neutral telechelics. Finally, we briefly describe recent work on creating block copolypeptide gels with unique rheological and self-assembly characteristics and new architectures for creating thermoreversible block polyelectrolyte gels.