Up to now, 3,4‐ethylenedioxythiophene (EDOT) or its modified analogs are indispensable units or subunits in all successful monomers for polythiophene synthesis through solid‐state polymerization (SSP). Here, a more open thiophene‐(CH(R))‐thiophene platform was developed successfully and corresponding poly(bis‐thiophene methine)s were obtained via C–C SSP or melt‐state polymerization (MSP), that is, bulk polymerization. Meanwhile, the observation of quite long effective Br–Br distance of 5.634 Å, which is more than 50% of halogen's double van der Waals radius (2rw), would help us to understand powerful capability of modulation of molecule movement and reaction under SSP. In addition, these polymers were further employed as acid sensors and they show highly sensitive response to HCl, MeSO3H, BF3‐OEt2, and HNO3. The detailed experiment reveals that P1 has the detection limit of 3.35 × 10−5 M for HCl. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1676–1683

EDOT–CH(R)–EDOT was chosen as a prototype model monomer for solid state polymerization (SSP). The aromatic moieties were first introduced in the branch chain in the polymer matrix.

We chose the three-atom linker EDOT–CH2–N(R)–CH2–EDOT as a large platform to determine boundary conditions through the introduction of a rigid or bulky moiety and to accurately control the SSP behavior.