Shiao-Hung Chiang Distinguished Seminar Featuring Dr. YuanQiao Rao, Penn State Behrend

How Processing Writes Polymer Structure: Nonequilibrium States, Hidden Observables, and Predictive Design Rules for Functional Materials Abstract Polymer performance is often governed not by molecular structure alone, but by the nonequilibrium states captured during processing. Because polymer chains are anisotropic, conformationally rich, and slow to relax, the steps that create a product—flow, cooling, stretching, drying, crystallization, cure, and interfacial interaction—can encode structural features that are difficult to observe directly yet decisive for performance. This seminar presents a framework for identifying these hidden observables and converting them into predictive design rules. In high-performance fibers, thermal and stress history are linked to paracrystalline disorder and mechanical response, which can be read through an iso-strain force–thermal test. In polymer nanocomposites, interfacial constraints suppress chain mobility until an interface behaves as an effective material phase. In transparent hardcoats, nanoparticle packing and defect populations determine whether glasslike mechanics can survive in a manufacturable coating. In membranes and biodegradable polymers, free volume, defectivity, and molecular accessibility govern transport, separation performance, and environmental fate. One question recurs across these systems: how do processing, interfaces, and molecular mobility create hidden polymer states, and how can those states be measured, modeled, and ultimately controlled? I will close with future directions in intelligent polymer processing, interface-controlled separations, and biodegradation-by-design. I will also reflect on Materials by Design as both a research methodology and a career framework: a way to turn real-world constraints into fundamental scientific questions, build collaborations across disciplines, and mentor students and early-career scientists to connect rigorous science with meaningful technological impact. Short