Molecular Aspects of Deformability in Printed Organic Semiconductors

The structural rigidity and electronic properties of semiconducting polymers are fundamentally influenced by their backbone geometry. As we push the boundaries of flexible and stretchable electronics for the next generation of sensing systems, understanding and controlling the physical and thereby the electronic structure of π-conjugated polymers becomes a crucial part of advancing these technologies. Rational design of new material compositions for energy-autonomous devices will require advanced theoretical approaches, including simulation of these material systems at the nano and micro scales with molecular dynamics (MD). However, due to the limitations of conventional methods like classical force fields, existing torsional scan (TS) methods for parameterizing inter-monomer torsional potentials fail to accurately represent the behavior of conjugated polymers with significant steric hindrance, leading to unusably distorted energy calculations. We introduce a more precise method based on isolating the energy associated with electron delocalization (DE) that decouples delocalization energy from other nonbonded interactions, providing more accurate estimates of backbone rigidity. Our method significantly improves the modeling of polymers like PNDI-T, demonstrating more accurate planarization energy calculations, and further allows for a general exploration of the difference in energy associated with electron delocalization between various backbone conformations. We extend our initial work to explore the effects of both dihedral and improper torsions on electronic properties. Our findings indicate that while improper torsion generally disrupts electron delocalization, certain configurations may enhance orbital overlap, reducing the energetic cost of certain conformations, suggesting pathways to maintain conjugation even under high torsional stress. This approach not only refines current computational models but also enhances the understanding of the mechanical and electronic behavior critical for developing advanced materials in flexible and stretchable electronics.