Synthesis and characterization of one-side polypyrrole coated conductive and flexible polyurethane films

Recently, conductive polymers have been the focus for scientists cause of wide application areas such as bio and chemical sensors, antistatic coatings, tissue engineering, rechargeable batteries, corrosion-inhibiting films and so on. Polypyrrole (PPy) is one of the most important conductive polymer cause of its advantages like, good electrical conductivity by its conjugated structure, relative ease to synthesis and oxidative stability compared with other conductive polymers. PPy can be synthesized by electrochemical or chemical oxidation polymerization of pyrrole (Py) in different kind of organic solvents and in aqueous media. On the other hand, polyurethane (PU) is one of the most multipurpose and useful engineering insulator polymer cause of its good mechanical properties. It is synthesized with using a prepolymer isocyanate, a polyol and a catalyst. That reactants have many different types to give to final PU product varied physical and chemical properties. In last decades, to improve individual materials' mechanical properties, to achieve products with high properties like resistance to environment, chemicals or flame or to obtain them in light weight with low costs, composite materials have been studied. There are also composite studies about PU and PPy combination. In this study, one-side PPy coated conductive and flexible PU/PPy composite films were synthesized in the acetonitrile (ACN)/H2O interface as a new alternative to two side coated PU films which have already reported in literature. Composite films were prepared by chemical oxidative polymerization method. First, PU flexible films were synthesized by the reaction of triol with the excess of isocyanate based prepolymer by using a catalyst and resulting PU has free reactive -NCO groups. Then, PPy was coated onto PU film by the reaction of aqueous solution of Py contacted to one side of the film, with cerium ammonium nitrate (CAN) in ACN contacted to the other side. Since, PU film had softened with ACN, the diffusion of Py into PU matrix become easier and PPy formation occured on the only ACN side of the film (PU/PPy). This PU/PPy composites were characterized by four-probe electrical conductivity, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscope (SEM) measurements. Mechanical properties of the composite films were obtained by Zwick Roell tensile tester. The thickness of PPy coating was determined as 0.015 μm by using polarized microscope imagines of cross section of composite. The glass transition temperature (Tg) was obtained as -60.38 °C and the highest conductivity of PPy side of PU/PPy composites was obtained as 3.5x10-4 S.cm-1, while the water side of PU film was still insulator.