Modular Synthesis of Fully Degradable Imine-Based Semiconducting p-Type and n-Type Polymers

Featuring acid-labile yet conjugated bonds along the polymer backbone, imine-based organic semiconductors are emerging as viable candidates for transient electronics. To enable their widespread use, a modular synthesis based on Stille cross-couplings is described herein. Compared to utilizing imine-based condensation, which is sensitive to interference from moisture, our approach offers relatively more control over batch-to-batch reactions. Notably, we show the molecular design and synthesis of an imine-and-thiophene-containing motif with dibromo or ditin functionality as building blocks for degradable semiconducting polymers. The building blocks can be readily copolymerized with aromatic units, which are commercially available or synthesized from well-established protocols, conventionally used in semiconducting polymers. In fact, such aromatic units are likely already available in laboratories synthesizing semiconducting polymers. In addition to degradable p-type semiconductors, we report the first degradable n-type semiconducting polymer. The degradable semiconductors are characterized by nuclear magnetic resonance, gel permeation chromatography, grazing-incidence X-ray diffraction, and ultraviolet-visible spectroscopy (UV-vis). The UV-vis spectra of their solutions and films resemble the spectra of their nondegradable vinyl analogues; still, we rationalize small differences between the band gaps with the assistance of density functional theory and time-dependent density functional theory. The charge carrier mobilities of the degradable p-type (0.28 cm(2)/V.s) and n-type (0.10 cm(2)/V.s) semiconductors also fare reasonably well with their nondegradable counterparts. These molecules enabled the fabrication of inverters, showing expected device characteristics. Given the ease and efficiency in the synthesis of the imine-containing building blocks and straightforward preparation of complementary building blocks for Stille cross-couplings, we anticipate this robust synthetic scheme to accelerate the exploration of imine-based degradable semiconductors.