Surface behavior and polymerization of 2-and 3-(1-octadecynyl)aniline at the air-aqueous interface

The surface behavior of 2- and 3-(1-octadecynyl)aniline (2ODA and 3ODA) was studied in Langmuir films and compared to that of 2- and 3-pentadecylanili ne (2PDA and 3PDA), which was previously reported. Surface pressure (Jr) an d potential (DeltaV) vs mean molecular area (A) isotherms of these substitu ted anilines were generated, and the results were, in part, attributed to t he orientation of the aromatic rings at the interface. Using well-establish ed methods, 2ODA and 3ODA were polymerized at the air-aqueous interface, an d the reactivities of the aniline derivatives were studied at different sur face pressures. It was found that the initial rate constant (k') for the po lymerization of 2ODA was significantly greater than that of 2PDA, but autoa cceleration was not detected. The reaction rates are explained in part by m olecular orientational differences at the air-aqueous interface. The polyme rization rates of 3ODA and 3PDA were comparable, which is probably due to s imilar headgroup orientation at the air-aqueous interface.