Langmuir and Langmuir–Blodgett films of N-(4-octadecyloxy-2-hydroxybenzylidene) derivatives of amino acids

Langmuir and Langmuir–Blodgett monolayers of N  -(4-octadecyloxy-2-hydroxybenzylidene) derivatives of glycine, tyrosine, and phenylalanine were studied using π–Aπ–A isotherms and photoelastic modulated FTIR (PEM-FTIR). Based on compression modulus and interaction parameters, mixed monolayers of these compounds with stearylamine (SAM) showed well-organized monolayers compared to mixed systems with stearic acid (SA) and stearyl alcohol (SAL). The pure amphiphiles exhibited fairly well-ordered packing in the films, and in the mixtures, the ordering increased and showed a triclinic packing arrangement. For the phenylalanine amphiphile the packing showed slight disorder compared to the other two compounds. Surface properties of the LB films of these compounds on solid substrates were analyzed using static and dynamic contact angles of a series of liquids. The surface tension of coated substrates reflected clearly the highly acidic character. Fluidlike monolayers having a molecularly rough surface indicated high wettability for n-alkanes. In contrast, the monolayer containing well-ordered, well-packed alkyl chains indicated low wettability and small hysteresis.

π–A isotherms and photoelastic modulated FTIR (PEM-FTIR) were used to characterize Langmuir and Langmuir–Blodgett films of N-(4-octadecyloxy-2-hydroxybenzylidene) derivatives of glycine, tyrosine and phenylalanine and their mixed films with stearic acid, stearyl alcohol and stearylamine. The mixed films exhibited increase in order compared to the pure amphiphiles and packed in a triclinic packing arrangement.Figure optionsDownload as PowerPoint slide