Langmuir-Blodgett mono- and multilayers of (di)alkoxy-substituted poly(p-phenylenevinylene) precursor polymers. 1. Langmuir monolayers of homo- and copolymers of (di)alkoxy-substituted precursor PPVs

The Langmuir monolayer behavior of (di)alkoxy-substituted precursor poly(p- phenylenevinylenes) (PPVs) with a methoxy-leaving group was studied. The av erage orientation of the aromatic ring and the ether groups at the air-wate r interface was elucidated by external F-T-infrared reflection spectroscopy measurements at the air-water interface combined with FT-IR computer simul ations. The aromatic rings of the precursors, except those of the dibutoxy- substituted one, take on, directly after spreading, an almost perpendicular orientation to the water subphase. The isotherms of these precursors showe d no special transitions, and these polymers can be considered to be in a c ondensed or 2-D collapsed state with lateral cohesive. pi-pi interactions b etween the aromatic rings as the most prominent interaction leading to this condensed state. The aromatic rings of the dibutoxy-substituted precursor are lying flat at the water surface at large areas per repeating unit and c an be considered to be in the expanded state directly after spreading. The isotherm of this precursor showed two transitions because here the chain co nformation is predominantly determined by the butyl chains and not by the m ain chain.