Molecular Design and Degradation Lifetimes of Semicrystalline to Near-Amorphous Degradable Semiconducting Polymers

Transient electronics have received widespread interest for their potential applications in reducing electronic waste and improving human health through implantable devices. Synthetic polymers serve as an attractive platform for the development of degradable electronic components due to their ability to be rationally tuned by molecular design for exploration of desired mechanical, electronic, and degradation properties. Although there has been much development on biobased and biodegradable insulating polymers for substrate and dielectric components in recent years, there are only several existing degradable semiconducting materials. As a result, the degradation behavior of semiconducting polymers in relation to molecular design as well as morphological and electronic properties has not been properly studied. Herein, we prepare imine-based semiconducting polymers with tuned polymer architectures, ranging from semicrystalline to near-amorphous morphologies, 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’ optical and morphological properties by ultraviolet-visible (UV-vis) spectroscopy, grazing-incidence X-ray diffraction, and atomic force microscope. By monitoring degradation via UV-vis, gel permeation chromatography, and NMR, we discover that polymer degradation in solution is heavily aggregation and hydrophilicity dependent. 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 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 implantable electronics with targeted, controlled lifespans.