The morphologies at elevated temperatures (T > T-g, T-m,) of 12 precise, polyethylene (PE)-based copolymers with acrylic acid (AA), phosphonic acid (PA), and 1-methylimidazolium bromide (1mBr) groups were studied via X-ray scattering. These precise copolymers enable direct comparisons focusing on the length of the spacer between the functional groups and the type of functional group. The polar groups in these materials self-assemble into microphase-separated aggregates dispersed throughout the nonpolar PE matrix. At high temperatures the PE segments are amorphous, such that the aggregates are distributed in a liquid-like manner in 11 of these precise copolymers. The correlation distances between aggregates increase with the following: carbon spacer length between pendant groups, size and volume fraction of the pendant species, and functional group configuration (single vs geminal substitution). In addition, comparisons are made between precise copolymers and pseudorandom copolymers of the same pendant concentration, wherein the interaggregate distances are much better defined with precise copolymers. Finally, the local packing in copolymers with geminal substitution of PA pendant groups is less compact, which might facilitate ion conduction.