Tuning the Degradation Lifetimes of Degradable Imine-Based Polymer Semiconductors by Molecular Design

Advancements in improving the electronic performance of degradable imine-based semiconducting polymers are pushing the field of transient electronics; however, our understanding of the structure-property relationships of this emerging class of polymers is very limited. Previously, we described a modular approach to prepare degradable semiconducting polymers by Stille cross-couplings. This facile method of polymerization enabled the preparation of both p-type and n-type imine-based donor-acceptor conjugated polymers, expanding the field of existing degradable semiconductors. While degradation studies confirmed the depolymerization into oligomers and monomers, the polymer degradation timescales and lifespans of the corresponding transient devices were not controlled. Comparisons of the degradation behavior across different imine-based semiconducting polymer architectures have also not been closely studied with respect to their morphological and electronic properties. Herein, we use Stille cross-couplings to rapidly prepare imine-based semiconductors with tuned polymer architectures for the systematic exploration of the impact of several molecular design parameters on the degradation lifetimes of these polymers. To rationalize differences in electronic performance and degradation behavior, we characterize the polymers by gel permeation chromatography, ultraviolet-visible (UV-vis) spectroscopy, and grazing-incidence X-ray diffraction. By monitoring degradation via UV-vis, we discover that polymer degradation in solution is aggregation dependent, with accelerated degradation rates facilitated by increasing the hydrophilicity of the polymers. Additionally, the aggregation-dependence of these degradable polymers rely heavily on the solvent used, with a fivefold difference in degradation time depending on solvent. We develop a new method for quantifying the degradation of polymers in the thin film and observe that similar factors and considerations used for designing high-performance semiconductors impact the degradation of imine-based polymer semiconductors. This study provides crucial principles for the molecular design of degradable semiconducting polymers, and we anticipate that these findings will expedite progress toward transient electronics with controlled lifetimes.