(1) background subtracted small angle X-ray scattering (SAXS) data from the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357, and the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Data is organized by polyelectrolyte complex micelles at investigated chain lengths. (2) autocorrelation functions from the dynamic light scattering (DLS) data in Figures 5 and S-9. Data is organized by scattering angle (Figure 5) or salt condition (Figure S-9) for each polyelectrolyte complex micelle system.