AbstractIn this paper, structural, electronic, and sensing properties of the poly(3‐methylthiophene) (P3MT) in two types of its core–shell nanocomposites with multiwall carbon nanotubes (MWCNTs) and poly(vinylidene fluoride) with different contents of the P3MT component (shell) are explored and are compared. The results indicate specific changes in the P3MT properties appear due to its interfacial interactions with the MWCNTs and PVDF components. In the case of the doped P3MT, charge transfer from MWCNT to P3MT leads to partial dedoping of the latter. The evidence of intermolecular charge transfer complex formation between undoped P3MT (donor) and MWCNTs (acceptor) is obtained. Changes in the properties of P3MT in nanocomposites are used to detect and to reliably recognize some chemical warfare agent's simulants of nerve agents and mustard gas. The sensitivity dependences of the nanocomposites on their work functions, Hansen solubility parameters and analytes electronegativity are studied. It is shown that the sensor response is controlled by a partial charge transfer if the difference between the work function of the sensing material and the electronegativity of the analyte molecules does not exceed a certain value (in the case herein ≈0.3 eV).