Mapping Self-Assembled Ternary Polymer Blend Phase Behavior Using Gradient Composition Libraries*

Blending block copolymers (BCPs) with homopolymers, other BCPs, or nanomaterials is a simple yet powerful way to tune self-assembled structure. However, mapping the composition-dependent phase behavior of polymer blends experimentally is a slow, laborious process resulting in coarse data sets. In response, we have developed a first-of-its-kind user tool that combines electrospray deposition with programmable motor control and gradient solution pumping to generate three-component compositionally graded thin film libraries on single substrates. We describe the creation of thin film libraries featuring blends of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) BCPs with PS and PMMA homopolymers, and demonstrate how synchrotron small angle X-ray scattering (SAXS) may be used to rapidly characterize the self-assembled domain morphology, spacing, and grain size as functions of blend composition and film thickness. This pairing introduces a high-throughput platform for autonomous characterization that promises to accelerate the discovery, design, and optimization of functional soft matter blends.