Self-assembled supramolecular structures of charged polymers at the graphite/liquid interface

The self-assembly of two anionic polymers on graphite was studied in situ u sing an atomic force microscope (AFM). One polymer (P4-Na) had a hydrophobi c phenylene backbone with hydrophilic sulfonate groups and hydrophobic dode cyl side chains. The other (diblock-P-Na) was a diblock copolymer: one bloc k had the same structure as P4-Na and the other block had anthracene groups on the phenylene backbones. AFM revealed regular supramolecular "ribbon" s tructures of P4-Na and of diblock-P-Na on graphite in a mixed solvent of wa ter and tetrahydrofuran (THF). The polymers adsorbed in two layers. The fir st 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 w ere much longer than the P4-Na ribbons. Solvent properties had a strong eff ect on the supramolecular structures of the two polymers.