Frustrating the lamellar ordering transition of polystyrene-block-polyisoprene with a C60 additive.

Thermal fluctuations in block copolymer (BCP) materials characteristically drive the ordering phase transition order from second to first order by the well known Brazovskii mechanism and there have been many observations of jumps in x-ray and neutron scattering intensity data at the order-disorder transition (ODT) that signal this phenomenon. However, the existence of quenched disorder can either destroy the ODT or restore the second-order nature of this type of phase transition. The present work considers how the dispersion of C(60) ("buckyballs"), which is prone to clustering in polymeric media, into poly(styrene)-block-poly(isoprene) to see how this nanoparticle additive alters the qualitative character of the BCP ordering. Small angle x-ray scattering indicates that a small amount (approximately = 1 mass %) of C(60) causes the BCP to remain disordered over a wide temperature range so that a phase transition no longer exists. This phenomenon offers both technological problems and opportunities.