Effect of C60 on the Morphology of Strongly Segregated ABC Miktoarm Terpolymers*

ABC miktoarm terpolymers place severe constraints on the configuration of immiscible polymer chains due to the joining at one junction point. We investigated the effect of C60 nanoparticles on a series of poly(styrene), poly(isoprene), poly(2-vinylpyridine) (PS-PI-P2VP) miktoarms by small angle scattering. To this end, we synthesized PS-PI-P2VP with symmetric PS and PI blocks and varied the degree of polymerization for P2VP. We denote the ratio between the volume fraction of P2VP and PS (or PI) as α. C60 addition leads to a reduction of the repeat period due, more than likely, to chain relaxation, in PS-PI-P2VP of the hierarchical lamellar morphology (HLM) which forms for α>∼2. In contrast, in a sample with a tiling morphology (TM) at short P2VP chains (α<1), we find the opposite behavior and the repeat period expands dramatically. We explain these distinct differences with the stability of the HLM (observed for ∼2>α>∼4) which thus appears rather insensitive to topological changes. In contrast, at all-symmetric conditions α=1 and below α<1 many TMs in close proximity are reported which means the morphology is susceptible to changes.