Mechanisms of polyaniline film formation via solution casting: Intra-chain contraction versus inter-chain association

•Mechanisms of formation of solution-cast films of polyaniline are dependent on the solution concentration.•Formation of “blue” films is due to entanglement of polymer chains of expanded conformation.•Formation of “violet” films is due to intra-chain compact coil conformation.•Higher amount of solvent residue, better protonation and absorption of analyte vapors for “blue” films.