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Block copolymers self-assemble into periodic morphologies with well-defined size and spacing having microdomains with characteristic length scales of a few to tens of nanometers and have been extensively studied due to their potential use as functional nanostructures. 1-6 The size and the type of the microdomains are dictated by molecular weight, volume fraction, segmental interactions, and molecular architecture of the blocks. 7, 8 The lower limit of microdomain sizes is set by segmental interactions, whereas mobility limits the largest sizes achievable. The addition of a homopolymer affords an attractive route by which the size scale of the nanodomains achievable with neat block copolymers can be extended. 9

Homopolymers with increasing molecular weight that are added to a block copolymer are more localized to the center of the microdomains, and if the molecular weight of the homopolymer is too large …