Programmable Electrostatics in Charge-Patterned Polypeptoid Micelles Probed by Small-Angle Neutron Scattering

Electrostatic interactions are key determinants in the assembly and organization of ionic micelles. Here, we synthesized sequence-defined polypeptoid block copolymers with discrete chain lengths and single or triple charged residues arranged in distinct patterns. Model-free small-angle neutron scattering analysis of semidilute polymer solutions at pH 9.0 revealed that intermicellar interactions follow screened Coulomb potentials, with strength and range determined by charge placement. Notably, positioning charged residues near the hydrophobic/hydrophilic block junction enhanced the range of electrostatic repulsion, while split-charge motifs produced stronger, longer-ranged repulsions than block-charge counterparts. Scattering length density profiles provide direct real-space insight into micellar dimension, core density, corona conformation, and solvent penetration. Micellar charge-to-aggregation number analysis further reveals the impact of invasive water and counterion association. This study demonstrates that sequence-specific charge patterning serves as a precise molecular tool for tuning micellar architecture and electrostatic interactions, establishing a foundation for programmable control of self-assembly in crowded environments.