Investigation of gel inhibitor assisted dissolution of polyaniline: A case study for emeraldine base, 2-methyl-aziridine, and N-methyl-pyrrolidone

The secondary amine 2-methylaziridine (2MA) is used as an additive together with N-methyl-2-pyrrolidone (NMP), to inhibit the gel formation of highly concentrated high molecular weight solutions of polyaniline (PANi) in the emeraldine base (EB) oxidation state for up to 29 hours room temperature. Rheological properties of concentrated EB (~ 20 wt%) solutions are studied by means of rotational viscometry as function of 2MA/EB molar ratio, time, shear rate, and temperature. Due to the formations of hydrogen bonds between the amine proton of 2MA and to lone electron pair from the imine nitrogens in the EB repeat unit. 2MA and NMP prevents the interactions between polymer chains which less to enhanced solubility, dramatic prolongation of times to gelation, and reductions in initial solution viscosity. The temperature effects on the gelation time and the activation energy for viscous flow are reported.