Special properties of monolayer formed by a novel Gemini amphiphile at air–water interface

A novel Gemini amphiphile, N,N′-bis-(4-decyloxy-2-hydroxybenzylidene)-ethane-1,2-diamine, was synthesized and characterized. This amphiphile is capable of forming stable monolayer at air–water interface. The limiting area has a minimum when the pH value of subphase is 12. The unique behavior is attributed to the formation of intramolecular hydrogen bond between hydroxyl groups. The existence of this hydrogen bond was supported by the FTIR results. With the addition of copper ion into subphase, the limiting area showed a decreasing value, which is quite different from that of the conventional neutral amphiphiles. XPS and UV–vis were also carried out to investigate the effect of copper ion on molecular area.