Rheokinetic Study of Concentrated High Molecular Weight Emeraldine Base in N-Methyl-2-Pyrrolidinone Solutions Containing 2-Methyl-Aziridine

Concentrated solutions of ultra-high molecular weight (HMW) emeraldine base (EB) are obtained when near stoichiometric quantities of 2-methyl-aziridine (2MA) per polymer repeat unit are co-dissolved in N-methyl-2-pyrrolidinone (NMP). Hydrogen bonds are formed between the secondary and tertiary EB nitrogen atoms found in the polymer repeat unit, and both the 2MA additive and the NMP solvent molecules. The rheological behavior of such solutions is quite different from that of EB/NMP solutions without 2MA. The principals of rheokinetic analysis are used to investigate the mechanism of the EB·2MA complex formation in the concentrated EB/NMP/2MA solution systems. The reaction rate, equilibrium constant and activation energy associated with the complexation are determined. Further, the stability of variable 2MA/EB molar composition and the kinetic effects due to variable temperature are reported for 20% (w/w) EB solutions.