Langmuir and Langmuir−Blodgett Films of a Phosphorus Derivative

Abstract

We have studied the ability of a novel molecule (diphenyl bis(octadecylamino) phosphonium bromide) to form both Langmuir films and Langmuir−Blodgett films under different experimental conditions. It has been found that this substance is capable of forming stable monolayers at the air−water interface and building up highly ordered LB films yielding Z-type LB films of high quality (transfer ratio of 1) which were characterized by UV−vis and IR spectra, electron microscopy, and X-ray diffraction.

Langmuir–Blodgett Films Containing TCNQ Incorporated from the Aqueous Subphase

“…The substrates (glass, CaF 2 , quartz, and Lindemann glass capillaries for the SEM, IR, UV-vis, and X-ray measurements, respectively) were cleaned thoroughly, as was previously described (2,27). The monolayers were transferred onto the substrates by the vertical dipping method.…”

“…In the latter case, the pressure increases again after the plateau and the area per molecule after it is one-half the area just before it begins. This plateau also appears in the isotherms of DPOP + when pure water is used as subphase and a detailed study of this phenomenon (27) concluded that the molecules suffered a rearrangement of the head groups (overshoot) and the formation of a bilayer (plateau). The experiments performed using LiTCNQ in the subphase (values of the area per molecule, hysteresis cycles, and the different slopes of the films absorbance vs numbers of layers transferred before and after the plateau) indicate that we are facing again the same situation as when pure water is used as subphase.…”

“…We have previously studied (27) the influence of the subphase nature, showing how it determines the isotherm shape, the stability of the monolayer, the transfer ratio, and the LB film quality. In this work we focus our attention on the second point, the influence of the TCNQ ·− concentration.…”

“…All this seems to indicate that the nature of the double ionic layer is quite different, and this means different molecular interactions and different rearrangements (different values of the area/molecule) that lead to monolayers showing different interactions among the molecules, different packaging (see later X-ray experiments and compare with DPOP in pure water (27)), and in consequence different physical properties. We will try to take advantage of this situation to prepare several types of LB films and to maneuver thin films into the desired properties.…”

“…DPOPBr is a molecule capable of forming very stable Langmuir films (27) and is easily transferable onto a solid substrate yielding to LB films to a highly ordered degree. Besides, the cation DPOP + has been used as a counterion in TCNQ salts (28)(29)(30)(31) with good conductivity values (although not arranged on LB films, but in a 3D salt).…”