Kinetically constrained block copolymer self-assembly a simple method to control domain size

In this work asymmetric polystyrene-block-polyethylene oxide (PS-PEO) diblock copolymers were blended with high and low molecular polystyrene (PS) homopolymer and spin cast, resulting in the rapid self-assembly of vertically oriented PEO cylinders in a matrix of PS. Due to the kinetically constrained phase separation of the system, increasing addition of homopolymer is shown to reduce the diameter of the PEO domains, even when the homopolymer was of significantly higher molecular weight than the PS block in the PS-PEO diblock copolymer and would be predicted to macro-phase separate from the copolymer. The outcomes of this study provide a novel method that requires the adjustment of a single variable to tune the size of vertically oriented PEO domains between 10 and 100 nm, with potential applications in a number of areas including membrane technologies.