Mechanical deformability underpins most of the advantages offered by polymeric semiconductors. A detailed understanding of the mechanical properties of these materials is crucial for the design and manufacturing of robust, thin-film devices such as solar cells, displays, and sensors. The mechanical behavior of polymers is a complex function of many interrelated factors that span multiple scales, ranging from chemical structure, to microstructural morphology, and device geometry. This thesis builds a multi-scale understanding of the thermomechanical properties of polymeric semiconductors through the development, and experimental-validation of computational methods for mechanical simulation. A predictive computational methodology is designed and encapsulated into open-sourced software for automating multi-scale molecular simulations on modern supercomputing hardware. These simulations are used to explore the role of molecular structure, processing conditions, and molecular weight on solid-state morphology and tensile behavior. Experimental characterization is employed to test these predictions— including the development of simple, new techniques for rigorously characterizing thin- film thermo-mechanics. Knowledge acquired from this fundamental research is employed to design a continuous manufacturing process: interfacial drawing, which leverages the spontaneous spreading and drying of a polymer solution at the surface of water to fabricate high-quality thin films over large areas.