Studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM) is the coaggregation of poly(tert-butyl acrylate)-block-poly(2-cinnamoyloxyethyl methacrylate), PtBA-PCEMA, and polystyrene-block-poly(2-cinnamoyloxyethyl methacrylate), PS-PCEMA, in mixtures of chloroform and hexane, where hexane is a precipitant for PCEMA and PS but a good solvent for PtBA. To ensure coaggregation, the PCEMA blocks in the different diblocks were tagged by the H-bonding DNA base pair thymine and adenine. Coaggregation of the associating diblocks resulted in interesting block copolymer aggregation behavior and morphologies.