Continuous Conjugated Polymer Network in Elastomer Matrix Arising from Solution-State Aggregation and Film-Forming Dynamics Favoring Mechanical and Electrical Properties

Abstract

The continuous conjugated polymer network structure in an elastomer matrix is significant for carrier transport. However, high-mobility conjugated polymers tend to form island-like phase separation. Here, a strategy is proposed to achieve a continuous conjugated polymer network structure via weakening the intermolecular interaction between the conjugated polymer chains and fast aggregation between conjugated polymer backbones during the film-forming process. This is enabled by hot spin-coating poly(2,5-bis(4-hexyldodecyl)-2,5-dihydro-3,6-di-2-thienyl-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thiophene) (PDPPT3) and polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) blend hot solution at 130 °C. In the solution state, PDPPT3 is observed to form small aggregates at 130 °C due to the decreased intermolecular interaction. In the film-forming process, these small aggregates grow rapidly and form a continuous network due to the enhanced polymer chain motion. In the meantime, the large-scale phase separation is suppressed by the short film formation time. Eventually, a sandwich-like vertical phase separation is generated, comprising a PDPPT3-enriched continuous network at both the top and bottom surfaces. Under strain, this small-scale phase separation PDPPT3 network can rotate freely and maintain sufficient connections for carrier transport. Finally, the optimized films exhibit 177% fracture strain and high average mobility of 0.99 cm² V⁻¹ s⁻¹ over 500 stretch-release cycles. This study offers a valuable approach for controlling morphology in blend systems.