Assembly of new amphiphiles with amide groups incorporated into the alkyl chain at the air–water interface

Members of a new class of amphiphiles 1–5 containing an amide group in the hydrocarbon chain have been synthesised by acylation of an amine with a carboxylic acid chloride. These compounds were studied by film balance measurements revealing that formation of stable monolayers at the air–water interface depends strongly on the position of the amide group. Three different types of surface pressure–area isotherms (π–A) isotherms were observed depending on whether the amide group is positioned close to the headgroup, in the middle or at the end of the hydrocarbon chain. Stable monolayers with condensed phases are only formed when the amide group is positioned close to the headgroup or at the end of the hydrocarbon chain. In the latter case, a two phase region is observed.