Thermodynamic properties of Langmuir layers created of monoimide perylenetetracarboxylic acid derivatives

Abstract

Langmuir films formed of some fluorescent dyes, 3,4-bis-pentyl ester of 9,10-N-(n-pentylimide)-perylenetetracarboxylic acid, as well as their mixtures with arachidic acid, were studied. Surface pressure versus mean molecular area isotherms for Langmuir films were reordered and the alignment of molecules at the air–water interface was estimated. The isotherms show that the dye molecules do not lie flat onto the water surface but are tilted with respect to the normal to the interface. The surface pressure–area isotherms of Langmuir films formed from the dye/arachidic acid mixture provide evidence for phase separation of the components within almost the entire range of mole fractions. A repulsive interaction between molecules was observed in all two components of Langmuir films.

Keywords:

• Langmuir films
• surface pressure–area isotherm
• perylene derivatives
• mixed monolayer

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a grant from the Polish Ministry of Sciences and Higher Education [06/64/DSPB/418] and the project ‘Engineer of the Future. Improving the didactic potential of the Poznan University of Technology’ [POKL.04.03.00-00-259/12], implemented within the Human Capital Operational Programme, co-financed by the European Union within the European Social Fund.