Coarse-Grained Modeling of P3HT:SBS Blends for Stretchable Organic Semiconductors

Understanding and predicting the mechanical behavior of conjugated polymer (CP) blend films are essential for developing flexible electronic devices. Here, we establish a coarse-grained (CG) molecular dynamics (MD) framework for poly(3-hexylthiophene) (P3HT) and styrene–butadiene–styrene (SBS) blends to elucidate their composition-dependent deformation mechanisms. Chemistry-specific CG potential parameters were systematically derived through force matching and Boltzmann inversion, enabling an accurate representation of both bonded and nonbonded interactions. Simulations reveal that increasing the P3HT fraction enhances strength and stiffness but reduces ductility, leading to a brittle fracture under tension. This behavior originates from the rigid π-conjugated backbone and dense chain packing of P3HT, which restrict chain mobility and limit energy dissipation during deformation. In contrast, SBS-rich blends retain rubber-like toughness, as the elastomeric network composed of flexible polybutadiene midblocks and polystyrene junctions effectively delocalizes stress and prevents localized fracture. Water-assisted tensile experiments, combined with STEM analysis, validated the CG model by reproducing composition-dependent stiffening and the transition from uniform to localized deformation, thereby confirming the direct link between blend morphology and the mechanical response. This integrated computational-experimental framework provides practical design guidelines for improving the mechanical durability of stretchable organic semiconductors.