Precise assembly of molecular chromophores assisted by proteins as scaffolds plays an important role in natural light-harvesting complexes in photosynthetic organisms such as plants and bacteria. Specifically, the intricate supramolecular organization of chromophores (e.g. chlorophyll dyes) on protein scaffolds leads to shift of light absorption to longer wavelengths, a characteristic phenomenon of J-aggregation, and promotes the efficient energy transfer at different size and time scales. Such J-aggregation has also been observed in a series of synthetic molecular chromophores, such as amphiphilic cyanine dyes in aqueous solution, as well as derivatives of perylene bisimides, porphyrins, 8, 9 chlorophylls, phthalocyanines, BODYPI, squaraines, and hydroazaacene dicarboximide . In addition, J-aggregates were also observed in the self-assembly of synthetic bacteriochlorins attached to peptides as a type of biohybrid light-harvesting systems. We have previously reported the aggregation behavior in a coilplate-coil molecule of pyrrolopyrrole cyanine (PPcy) derivative in the co-precipitation with a polymeric surfactant in a mixture of tetrahydrofuran and water. The flash precipitation of PPcy in water resulted in the formation of both H-and J-aggregates together with some monomers. Nevertheless, the effects of chemical structures and molecular weights of synthetic polymers as scaffolds on Jaggregation coupling of molecular chromophores remain poorly understood. Studies to address these issues are important to realize a rational molecular design of synthetic chromophore/polymer complexes for applications such as artificial photosynthesis and biomedical applications.