Softness and mechanical deformability underpin most of the advantages offered by semiconducting polymers. 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 molecular structure, to microstructural morphology, and device geometry. This thesis builds a comprehensive understanding of the nanoscale thermomechanical properties of polymeric semiconductors through the development and experimental-validation of computational methods for molecular dynamics simulation. A predictive computational methodology is designed and encapsulated into open-sourced software for automating molecular simulations on modern supercomputing hardware. These simulations are used to explore the role of molecular structure/weight and processing conditions on solid-state morphology and thermomechanical behavior. Interestingly, we find that semiconducting polymers are more appropriately modeled as ribbon-like chains than worm-like chains. 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.

Mechanical properties of semiconducting polymers: From molecular simulations to process design

256th National Meeting (2018)

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