Statistically Enriched Adjacent Cationic–Aromatic Motifs Enable Reversible Shear-Induced Gelation in Aqueous Polymer Solutions

Protein mechanical responses are governed not only by dynamic noncovalent interactions but also by their local sequence organization. Inspired by this principle, we study a hydrophobic polyelectrolyte with a statistically enriched neighboring distribution of cationic and aromatic monomers. In water, concentrated solutions of this polymer undergo reversible shear-induced gelation, transforming from viscous liquids into transient gel-like states under shear and recovering fluidity after the removal of stress. This transition depends strongly on concentration and shear rate, indicating a concentration-dependent entangled state that becomes increasingly susceptible to network formation under flow. A nonaromatic control polymer does not exhibit this behavior. In saline media, electrostatic screening drives the system into a salt-induced associated state, yet the reversible shear-induced transient gel-like transition persists. The gelation transition and the dimensions of rodlike aggregates both depend on the identity of the added alkali metal cation. Because this ion dependence follows the known aqueous cation−π competition trend, the results identify cation−π interactions as the dominant sequence-specific driving force. These findings show that statistical enrichment of neighboring cation–arene motifs can encode protein-like force responsiveness in synthetic polymers.