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A longstanding challenge in the field of optoelectronic materials, the effects of solid-state arrangement and morphology are still a prominent factor associated with small-molecule and polymer-based device performance. Here, mixed heterocyclic aromatic oligomers containing thiophene, furan and pyrazine are prepared alongside their methylated congeners. Their solution and solid-phase properties were studied via spectroscopic, electrochemical and single-crystal X-ray diffraction (XRD) analysis. Comparative analysis between solid-state packing arrangements and photophysical properties revealed optical band gaps as low as 1.7 eV with Stokes-shifts up to 130 nm and quantum yields of 12%. Results of the study aid in further understanding the effects of molecular and solid-state arrangements that give rise to unique optical and photophysical properties critical to enhancing optoelectronic behavior. 

Thermal chemical synthesis of conjugated polymers has often been plagued by low product yields, by-product contamination and high-cost catalysts. Electrochemical synthesis is an alternative strategy that can overcome these failures to obtain highly efficient syntheses. Herein, we present the study of diketopyrrolopyrrole-bisthiophene (DPPT 2 ), diketopyrrolopyrrole-bisfuran (DPPF 2 ) and thienothiadiazole-bisthiophene (TTDT 2 ) for diblock copolymerization with terthiophene (T 3 ) as a π-linker to form tunable narrow band gap polymers. The polymers suspended as thin films have similar redox characteristics to the monomers with potential shifts that prove the identity of the respective polymers. Electrochemical impedance measurements were carried out in the −0.6 V to 1.0 V potential range with an average electron transport resistance ( R e ) value of 110 Ω irrespective of the applied potential. This confirms the polymers to have higher intrinsic electrical conductivity. The atomic ratios of the synthesized materials were calculated experimentally using energy dispersive X-ray (EDX) analysis, and they confirm the theoretical composition of the polymers. These doped polymers exhibit absorption bands in the visible to SWIR region (800–1800 nm) with optical band gaps from 0.773 to 1.178 eV in both the solid and the solution state. 

Block copolymers comprising benzothiadiazole were successfully electro-copolymerized leading to (BTD-T 2 ) n (BTD-F 2 ) m , where n and m were varied in a perfectly controllable, well-defined manner. The polymers were characterized by cyclic voltammetry, AC-impedance, SEM–EDAX and XPS analyses. They exhibit absorbance and emission in the near infrared (NIR) region. Results support an efficient strategy towards the creation of even more complex materials with innumerable possible applications in optoelectronic. 

Thienothiadiazole‐bisthiophene (TTDT₂) and diketopyrrolo–pyrrole–bisthiophene (DPPT₂) are successfully electro‐copolymerized with terthiophene (T₃) as an initiator and linker at low oxidative potentials. AC impedance analysis, absorption spectroscopy, and elemental composition via SEM‐EDX support the formation of donor–acceptor (D–A) type alternating block copolymers, poly(T₃‐TTDT₂), and poly(T₃‐DPPT₂). Unique optical properties that span into the near infrared‐II(>1000 nm) region and inherent electrical conductivity at the p‐type regime, n‐type regime, and in between the two regimes (i.e., typical insulator region) are observed. This study showcases the advantages of electro‐polymerization toward tailoring of next generation opto‐electronic materials.