A Comparative Study of the Effects of Rinsing and Aging of Polypyrrole/Nanocellulose Composites on Their Electrochemical Properties

Abstract

The effects of polymerization conditions, rinsing, and storage on composites composed of polypyrrole (PPy) and Cladophora nanocellulose in terms of purity, chemical composition, conductivity, and electroactivity were investigated using conductivity measurements, cyclic voltammetry, FTIR-ATR, XPS, and ICP-AES. A clear correlation between rinsing volume and PPy degradation was found using water- or NaCl-rinsing solutions as evidenced by conductivity and electroactivity losses. It was further found, through FTIR-ATR as well as XPS-measurements, that this degradation was caused by incorporation of hydroxyl groups in the PPy-layer. The extent of degradation correlated with a shift in the FTIR-ATR peak around 1300 cm^–1, showing that FTIR-ATR may be used as a quick diagnostic tool to evaluate the extent of degradation. By the use of acidic rinsing solution, this degradation effect was eliminated and resulted in superior samples in terms of both conductivity and electroactivity and also in a more efficient removal of reactants. Upon ambient storage, over a period of 200 days, a gradual decrease in conductivity was found for initially highly conductive samples. The electroactivity, on the other hand, was relatively unaffected by storage, showing that conductivity measurements alone are ineffective to determine the degree of polymer degradation if the water content is not controlled. Also, FTIR-ATR measurements indicated that the oxidation state did not change to any large extent upon storage and that only minor degradation of PPy occurred. The results presented herein thus offer valuable guidelines on how to develop simple and reliable postsynthesis treatments of conducting polymer–paper composites with performance fulfilling requirements on stability, electroactivity, and purity in applications such as environmentally friendly energy storage devices and biomedical applications