Complexes of an anionic poly(p-phenylene) polyelectrolyte and dioctadecylammonium bromide at the air-water interface

By spreading dioctadecyldimethylammonium bromide on a subphase containing r igid rod-like anionic poly(p-phenylene) sulfonate, a complex monolayer is f ormed in situ at the air-water interface. Complexation results in an increa se of the area per amphiphile molecule compared to the amphiphile on pure w ater. The change in structural order upon complexation and subsequent compr ession of the monolayer can be demonstrated employing UV/Vis spectroscopy: A red-shift of the polymer absorption band upon compression and a subsequen t partial reversion of this shift after monolayer collapse can be observed. The peak shift is discussed to be a result of the electronic interaction o f the pi-systems (aggregation) or to be due to a planarisation caused by ch anges in intramolecular and intermolecular interaction upon complexation an d compression. Both explanations require the formation of a highly ordered monolayer structure with increasing surface pressure. Upon collapse of the monolayer, the structure relaxes. Investigation of the complex Langmuir-Blo dgett (LB) films employing UV/Vis spectroscopy gives further information ab out the structural order. XPS measurements reveal that a stoichiometric com plex is formed. (C) 1999 Elsevier Science S.A. All rights reserved.