Synthesis of Dioxythiophene-Based Conjugated Polymers via Living Direct Arylation Polymerization and Construction of Bottlebrush Architectures

Bottlebrush polymers featuring electroactive conjugated poly(dioxythiophene) structures represent a distinct class of nonlinear polymers with promising applications in organic devices. Herein, we synthesized a norbornenyl-functionalized palladium(II) complex 2 as an initiator for the polymerization of dioxythiophene monomers via living direct arylation polymerization. The resulting polymers were characterized via nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, confirming well-defined structures. A macromonomer bearing a terminal norbornene group underwent ring-opening metathesis polymerization (ROMP) with the third-generation Grubbs catalyst (G3), enabling the formation of bottlebrush polymers via a “graft-through” strategy. Alternatively, in the “graft-from” approach, norbornenyl-functionalized palladium(II) complex 2 was first polymerized via ROMP to afford a poly(norbornene) macroinitiator, which subsequently initiated the polymerization of dioxythiophene monomers, yielding brush polymers with poly(norbornene) backbones and polydioxythiophene side chains. Atomic force microscopy and transmission electron microscopy revealed that the resulting brush polymers formed worm-like aggregated morphologies. The presence of Pd(II) complex at the chain ends enabled further chain extension, successfully yielding block bottlebrush copolymers. Moreover, films of bottlebrush polymers with electroactive conjugated polydioxythiophene exhibited an electrochemical color change from red to a highly transmissive sky-blue oxidized state.