The Evolving Landscape of Polymer Glass Transition and Dynamics for Flexible and Semirigid Polymers

ABSTRACT The glass transition temperature ( T g ) and underlying segmental dynamics are fundamental parameters governing the thermomechanical and macroscopic properties of polymeric materials. Honoring the 65th birthday of Professor Sindee L. Simon, this perspective first highlights several of her pioneering contributions to the understanding of structural recovery and nanoconfinement in polymers, using Flash differential scanning calorimetry (Flash DSC). While physical confinement heavily dictates the behavior of traditional linear polymers, semirigid conjugated polymers, the cornerstone of modern flexible electronics, experience an intrinsic “self‐confinement” arising from nanoscopic domains between their highly rigid backbones and packed, flexible side chains. This unique architecture yields extreme dynamic heterogeneity and vanishingly small heat capacity changes (Δ C p ), rendering traditional DSC largely ineffective. Inspired by Professor Simon's methodologies, this perspective will describe how the application of Flash DSC to conjugated polymers successfully overcomes these kinetic and thermodynamic barriers, isolating elusive thermal transitions. We explain how understanding and manipulating polymer dynamics directly impacts macroscopic device engineering: from maintaining viscoelastic mechanical compliance in soft wearable electronics to engineering stable organic photovoltaics. Finally, we highlight the necessity of a multi‐modal approach, coupling Flash DSC with the microscopic structural resolution of neutron scattering to fully map the evolving dynamic landscape of conjugated polymers.