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

Abstract

The Langmuir monolayer behavior of (di)alkoxy-substituted precursor poly(p-phenylenevinylenes) (PPVs) with a methoxy-leaving group was studied. The average orientation of the aromatic ring and the ether groups at the air-water interface was elucidated by external FT-infrared reflection spectroscopy measurements at the air-water interface combined with FT-IR computer simulations. 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 showed no special transitions, and these polymers can be considered to be in a condensed or 2-D collapsed state with lateral cohesive π-π interactions between 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 can be considered to be in the expanded state directly after spreading. The isotherm of this precursor showed two transitions because here the chain conformation is predominantly determined by the butyl chains and not by the main chain.

Oxidation of Monolayers of Partly Converted Dimethoxy-Substituted Poly(p-phenylenevinylene) Precursor Polymers at the Air−Water Interface

“…The preparation of precursor polymer poly[2,5-di-methoxy-1,4-(R-methoxy)xylylene] (prec-DMePPV) (see Scheme 1) was described previously. 1 Party converted DMePPVs were prepared by dissolving 300 mg (1.5 mmol) prec-DMePPV in 30 mL 1,2,4-trichlorobenzene. This solution was degassed and allowed to reflux under an inert nitrogen atmosphere.…”

“…1,2 The precursor polymers formed true 2D stable monolayers at the airwater interface in which all polymer segments are in contact with the water subphase. Immediately after spreading, the aromatic rings of dimethoxy-substituted precursor (prec-DMePPV) take on a more-or-less perpendicular orientation to the surface, and the monolayer is about 8 Å thick.…”

Langmuir–Blodgett films of helical rigid-rod poly(quinoxaline-2,3-diyl)s

“…This suggests that perfectly linear-shaped polymer backbones, for example, rigid-rod-like polymers and extended forms of flexible polymers, are highly suitable for the formation of stable LB films, as such linear-shaped polymers can be packed effectively in the two-dimensional water surface. [6][7][8][9][10][11] In fact, one of us found that poly(N-alkylacrylamide)s adopted a perfectly extended, zigzag conformation in stable LB films, in spite of the fact that the polymer was conformationally flexible in solution. 4,12 We have developed a new chemistry of poly(quinoxaline-2,3-diyl)s that are prepared by the living polymerization of 1,2-diisocyanobenzenes.…”

“…This suggests that perfectly linear-shaped polymer backbones, for example, rigid-rod-like polymers and extended forms of flexible polymers, are highly suitable for the formation of stable LB films, as such linear-shaped polymers can be packed effectively in the two-dimensional water surface. [6][7][8][9][10][11] In fact, one of us found that poly(N-alkylacrylamide)s adopted a perfectly extended, zigzag …”

In-Plane Orientation in Langmuir−Blodgett Multilayers of a Partly Converted Flexible Poly(p-phenylenevinylene) Precursor Polymer

“…10,11 The advantage of this precursor polymer is that the leaving group is much smaller. Therefore, it is expected that the leaving group causes less damage to the multilayer structure when the precursor polymer is converted to PPV by heat treatment.…”