Modulating Water Distribution and the Intramicellar Assembly of Sequence-Defined Ionic Peptoid Block Copolymers by the Ionic Monomer Position

The intramicellar mass heterogeneity of a series of sequence-definedionic peptoid block copolymers carrying a single charged monomer hasbeen determined through contrast variation small-angle neutron scatteringanalysis. We observe that the internal micellar structure, namely,the number density radial distributions of invasive water and peptoidpolymer, is significantly impacted by the location of the ionic monomer.By positioning the ionic monomer progressively closer to the hydrophilic/hydrophobicblock junction, the micelles become less compact with increasing levelsof chain folding and invasive water to accommodate electrostatic repulsionamong the ionic monomers via solvation. This results in increasinglysmaller micellar aggregates with aggregation numbers (N (agg)) ranging from 15.6 to 44 and micellar radii (R (b)) ranging from 61 to 94 & ANGS;. This studyhighlights the potential of using ionic monomer position as a designparameter to control the internal structures of nanoscale micellarassemblies.