We investigated the pH-directed self-assembly of Tetronic 304 (T304), an amphiphilic four-arm block copolymer of interest for application in drug delivery systems. While T304 and its analogues have been investigated regarding their pharmaceutical and therapeutic applications, a fundamental understanding of their pH-directed self-assembly is lacking. Integrating unbiased molecular dynamics simulations with small-angle neutron scattering and dynamic light scattering experiments provided an unprecedentedly detailed interpretation of our experimental findings and also directed the selection of suitable models for experimental data analysis. We subsequently probed the interactions that drive and hinder the self-assembly of T304 at the atomistic level of detail. pH-driven conformation changes in the central ethylenediamine group of T304, and subsequent interactions with water, ultimately drive the self-assembly of T304 and the structure of the resulting polymeric micelles. Our work provides detailed mechanistic understanding of pH-directed polymer self-assembly and supports the rational design of new pH-responsive functional polymer materials.