Impact of imine bonds on the electronic properties of degradable carotenoid-based conjugated polymers†

Abstract

Carotenoids are suitable building blocks for degradable π-conjugated polymers due to their intrinsic single-molecule conductance and well-documented degradation pathways. Previously, we reported a carotenoid-based polymer, p(CP-hexyl), which incorporated a cleavable imine linker enabling degradation via acid hydrolysis or sunlight; however, there was limited insight into its electronic properties. In this current study, we compare the optoelectronic and photophysical properties of p(CP-hexyl) with a structural analog, caro-PPV, which replaces the imine bonds with vinylene groups, to improve charge transport while maintaining degradability. Ultraviolet–visible spectroscopy, density functional theory, and transient absorption spectroscopy provided a comprehensive understanding of these polymers’ optoelectronic properties. Further, chemical doping and oxidative degradation were evaluated using FeCl₃ and trifluoroacetic acid, unveiling differences in radical formation and degradation mechanisms for both carotenoid-based polymers. Lastly, charge carrier mobility measurements in organic field-effect transistors unveiled caro-PPV's superior semiconductor performance, with mobilities 10³–10⁴ times greater than p(CP-hexyl). These findings highlight the potential of carotenoid monomers in the design of π-conjugated polymers for degradable electronics.