Thermal transitions and mechanical properties of films of chemically prepared polyaniline

The mechanical and thermal properties of the solution-cast films of chemically prepared polyaniline have been studied by means of dynamic mechanical analysis (d.m.a.), differential scanning calorimetry (d.s.c.) and thermogravimetric analysis (t.g.a.). The glass transition temperature (Tg) of the polyaniline films in emeraldine base form was determined and characterized for the first time to be in the range of ∼ 105–220°C for the films containing ∼ 16-0% of 1-methyl-2-pyrrolidinone (NMP) residual solvent, respectively, from a decrease in the storage modulus in d.m.a. and from d.s.c. studies. Depending on the content of NMP, the thin films of polyaniline have a storage modulus of ∼ 200 MPa-2 GPa at temperatures below Tg. Other thermal transitions and reactions in the temperature range of ∼ 25–500°C are also characterized by infra-red spectroscopy, X-ray diffraction and cyclic voltammetry and are discussed in relation to the mechanical properties of polyaniline.