Finite-Size Networks from Cylindrical Polyelectrolyte Brushes and Porphyrins

We report on the electrostatic self-assembly of negatively charged cylindrical polystyrenesulfonate (NaPSS) brushes and stiff organic counterions of different valency. In particular, the tetravalent cationic porphyrin meso-tetrakis(4-(trimethylammonium)phenyl)porphyrin (TAPP) yielded two new supramolecular architectures that are stable in aqueous solution. The porphyrin binds to the polyelectrolyte brush due to electrostatic and secondary pi-pi interactions and can further interconnect the brushes to nanoscale networks. In salt solution individual porphyrin-decorated cylindrical brushes were obtained. Structures formed are characterized by UV-vis spectroscopy, atomic force microscopy (AFM), cryo-transmission electron microscopy (cryo-TEM), small-angle neutron scattering (SANS), and dynamic light scattering (DLS). In order to study porphyrin aggregates by DLS, an IR laser setup (lambda = 831.5 nm) was used. The new morphologies have potential as functional structures in molecular electronics and pharmaceutics.