LAUSR

Significance Control of self-assembled structures of charged macromolecules in aqueous solutions is vital in myriads of natural phenomena. In the simplest situation, uniformly charged polyelectrolyte chains in electrolyte solutions are homogeneously distributed due to their electrostatic repulsion. In stark contrast to this well-established result, we find that the same system exhibits rich phase behavior consisting of precipitation, an interlude of self-assembled mesomorphic structures that can self-poison, and homogeneous solution, in the presence of a small organic anion. Using conceptual arguments, our experiments reveal that this phenomenon originates from dipole–dipole interactions overwhelming charge–charge repulsion. The discovered principle of dipole-directed assembly is essential to understand and control macromolecular structures in the broader context of polyzwitterions, polyelectrolyte–surfactant complexation, coacervation, and membraneless organelles.