Autoxidative oligomerization of an amphiphilic aniline in monolayers at the air-water interface

An amphiphilic aniline derivative, 2-octadecyloxyaniline, spontaneously oligomerized in monolayers at the air-pure water interface by oxygen contained in air and/or water. The rate constant at the beginning of the oligomerization was estimated to be 0.003 min(-1). The conversion reached 80% after 3 h under the constant molecular area (greater than or equal to 45 +/- 5 Angstrom(2) molecule(-1)). Maximum chain length of the oligomer was 5 monomer units. The UV absorption spectrum of each oligomer separated by GPC was red-shifted with increasing chain length. The monolayer oligomerization occurred even on the strong basic aqueous subphase (pH 12) with relatively high conversion (50-80%). The LB multilayer transferred onto the substrate showed a highly ordered layered structure, which was evidenced by TEM and XRD.