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

Carotenoids are ideal 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 (UV-Vis) spectroscopy, density functional theory (DFT), and transient absorption (TA) spectroscopy provided a comprehensive understanding of these polymers’ optoelectronic properties. Further, chemical doping and oxidative degradation were evaluated using FeCl3 and trifluoroacetic acid (TFA), unveiling differences in radical formation and degradation mechanisms for both carotenoid-based polymers. Lastly, charge carrier mobility measurements in organic field-effect transistors (OFETs) 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.