The influence of zinc phthalocyanine on the formation and properties of multiwalled carbon nanotubes thin films on the air–solid and air–water interface

•The repulsive interactions appeared as a result of the interactions of tert-butyl groups of PC with MWCNT.•The attractive interactions were a consequence of the interaction of the PC macrocycle with MWCNT.•Determination of the fraction of area covered with MWCNT based on the Π-A isotherms.•Determination of percolation threshold expressed as mass fraction, surface density and surface fraction covered by MWCNT. The influence of zinc phthalocyanine (PC) on the formation and properties of multiwalled carbon nanotube (MWCNT) Langmuir films was studied. The mixtures of PC and MWCNT at different concentrations were prepared and used to obtain films on the air–solid and air–water interface. The excess Gibbs energy, excess areas and the area fraction covered by the mixtures components were determined for mixed systems at various surface pressures. For the mass fractions of MWCNT lower than 0.9, the interactions between the mixture components were attractive, while for the MWCNT mass fractions higher than 0.9, they were repulsive. Analysis of the area fractions and fluorescence images revealed three stages of filling the MWCNT films with PC. In the first stage, the PC filled the area between the MWCNT and started to form inclusions in the MWCNT film structure. In the second stage, gradual increase in the PC inclusion size with increasing PC concentration was observed. In the third stage, continuous PC films were formed. These observations were further confirmed by the calculation of electrical percolation threshold.