Carboxymethylcellulose: A conductivity enhancer and film-forming agent for processable polypyrrole from aqueous medium

The use of carboxymethylcellulose (CMC) in polypyrrole (PPy) synthesis and in the production of PPy freestanding films was investigated. PPy was synthesised by chemical oxidative polymerisation in aqueous solutions using ammonium persulfate (APS) as oxidant and CMC as conductivity enhancer (CMCd). CMCs with different molar weight, namely 90,000 and 250,000 g/mol, were tested. The influence of polymerisation temperature, time, and CMC concentration, on the conductivity of PPy was evaluated thus showing that higher conductivities were obtained at low temperature, short polymerisation time and in the presence of low molar weight CMC. A long time polymerisation study was carried out at 3 °C and 24 °C revealing the presence of a double regime polymerisation process, with second regime rates depending on the polymerisation temperature.CMC was also used to improve the limited film forming ability of PPy by dispersing preformed PPy particles in CMC aqueous solutions. When decreasing the weight fraction of film forming CMC, semiconducting, flexible and freestanding films with thickness of 50–100 μm were obtained and their conductivity increased proportionally to the CMC weight fraction.

Research highlights▶ Carboxymethylcellulose (CMC) enhanced the conductivity of chemically synthesised PPy. ▶ The higher the CMC molecular weight the lower the PPy conductivity. ▶ Presence of a two regimes polymerisation process in PPy–CMC–APS systems at both 3 and 24 °C. ▶ An inverse relationship between polymerisation yield and electrical properties was found. ▶ Elaboration of CMC–PPy conducting films using CMC as conductivity enhancer and film forming agent.