The self-assembly of two anionic polymers on graphite was studied in situ using an atomic force microscope (AFM). One polymer (P4-Na) had a hydrophobic phenylene backbone with hydrophilic sulfonate groups and hydrophobic dodecyl side chains. The other (diblock-P-Na) was a diblock copolymer: one block had the same structure as P4-Na and the other block had anthracene groups on the phenylene backbones. AFM revealed regular supramolecular "ribbon" structures of P4-Na and of diblock-P-Na on graphite in a mixed solvent of water and tetrahydrofuran (THF). The polymers adsorbed in two layers. The first layer adsorbed quickly, and was composed of features two molecules wide and several to hundreds of molecules long, which were arranged in domains. The second layer adsorbed more slowly and was composed of ribbon structures with a similar substructure to the first layer. The diblock-P-Na ribbons were much longer than the P4-Na ribbons. Solvent properties had a strong effect on the supramolecular structures of the two polymers.