Phase behavior of the melt of polystyrene-poly(ethylene oxide) metallo-supramolecular diblock copolymer with bulky counterions

The melt morphology of polystyrene-poly(ethylene oxide) metallo-supramolecular diblock copolymer has been investigated using small-angle X-ray scattering. The two polymer blocks are linked via a bis(terpyridine)ruthenium(II) ion complex, and tetraphenylborate counterions are used to neutralize the copolymer. A highly ordered lamellar melt with a period of 11.9 nm is obtained by annealing at 55 degrees C for 40 h. The lamellar structure is composed of segregated domains of the polystyrene and polyethylene blocks with the metal ions and their associated counterions confined to the lamellar interfaces. The lamellar structure disappears during a subsequent heating at 80 degrees C, leading to a disordered melt. This morphology differs from the spherical aggregates exhibited by the same copolymer melt with smaller hexafluorophosphate counterions, whereby the melt organized into spherical aggregates' which underlines the role of the counterions in tuning the final morphology of such supramolecular diblock copolymers.