Electrical/Spectroscopic Stability of Conducting and Biodegradable Graft-Copolymer

Development of conductive and biodegradable graft-copolymers is decisive for applied electrical biointerfaces. However, to make significant breakthrough in bioelectronics, addressing changing properties while degrading is essential. Herein, the conductive and biodegradable poly(3,4-ethylenedioxythiophene) and poly(D,L-lactic acid) copolymer (PEDOT-co-PDLLA) submitted to 35 days of degradation in either deionized water or phosphate-buffered saline (PBS) is reported. Cyclic voltammetry, electrochemical impedance spectroscopy, and Raman microspectroscopy are used to correlate the electrical stability with molecular/structural changes during the degradation process. Two different proportions 1:05 (higher PEDOT content) and 1:50 (lower PEDOT content) are evaluated. The PEDOT-co-PDLLA 1:05 presents stable charge storage capacitance (CSC) in PBS for 35 days. PEDOT-co-PDLLA 1:50 shows an enhanced CSC when freshly prepared. However, it promptly loses its capacitance. Raman spectroscopy demonstrates that 1:05 as-prepared shows mostly neutral state. Nonetheless, after 35 days of degradation, both graft-copolymers show similar spectra, with contributions of oxidized states. Although the increase in oxidized states moieties should improve the conductivity, its dependence on interconnectivity and its relevance to remaining electronically stable, intrinsically related to conductive/biodegradable proportions in as-prepared graft-copolymer are demonstrated. This work contributes to a better understanding of the electrical stability of graft-copolymers for designing smart devices in bioelectronics applications.