New 1-acyl-1,2,4-triazoles (ATs) with different n-alkyl chain lengths from C2 to C18 were synthesized. ATs with long n-alkyl chains (C12 and larger) are non-charged amphiphilic molecules with a polar triazole head group. The Langmuir isotherms of ATs at the air-water interface with 12 (DoT-C12), 14 (MyT-C14), 16 (PaT-C16) and 18 (StT-C18) carbon atoms in their n-alkyl chains were studied using surface pressure-mean molecular area (pi-mmA) measurements. Characteristic for the Langmuir isotherms of PaT-C16 and StT-C-18 was the first sharp increase of the surface pressure at a mmA value of similar to 20 angstrom(2) marking a transition of the ATs from the gaseous state with n-alkyl chains already oriented perpendicular to the water Surface to a condensed state. The collapse of the monolayers occurred between 20 and 36 mN m(-1) with a typical 'spike' in the isotherms of MyT-C14, PaT-C16 and StT-C18 which can be assigned to the buckling and subsequent folding of the monolayer. After the collapse point a pseudo-plateau region of slightly increasing surface pressure appeared for all ATs from Cl 2 to C18 indicating a tri-layer formation by the roll-over mechanism for MyT-C14, PaT-C16 and StT-C18. Upon further compression the final collapse occurred at pi values between 59 and 67 mN m(-1). From reversibility studies it was found that the Langmuir isotherms of the ATs were irreversible. The Morphology of Langmuir-Blodgett films of ATs transferred onto silicon wafers was Studied by atomic force microscopy. (C) 2009 Elsevier Inc. All rights reserved.