Molecular variables in the self-assembly of supramolecular nanostructures

Supramolecular structures have the potential to provide macromolecular behavior using relatively low molar mass building blocks. We present here data on the self-assembly of triblock rodcoil molecules which contain a rigid biphenyl ester segment covalently linked to structurally diverse oligomeric segments. These molecules form supramolecular aggregates with molar masses in the range 10⁵-10⁶ Da, and our experiments probe how supramolecular structure can be manipulated by varying the volume fraction of the coillike flexible segments with respect to that of rod segments. The oligostyrene-oligoisoprene diblock coils were synthesized via anionic polymerization and varied in average length from (6_sty, 6_iso) to (30_sty, 30_iso). Small-angle X-ray scattering scans revealed layer spacings corresponding to monolayers that increase in size as the coil's molar mass increases. We observed that an increase in coil volume fraction reduces the thermal stability of the supramolecular structure, but a corresponding increase in rod segment length can counteract this effect. Finally the self-organized nanostructures seem to pack into a superlattice based on evidence obtained by X-ray scattering and transmission electron microscopy.