LANGMUIR-BLODGETT FILMS OF CPs

A rather unique method of processing CPs is in the form of Langmuir-Blodgett (LB) films), and many studies have been carried out to date in this area. Before describing some of these, however, it is pertinent to note that they appear to be primarily of scientific interest, as the exact practical utility of such LB films is still unclear. Although many claims of greater molecular order, greater conductivity, and other such properties have been claimed, these have not been substantiated by the studies thus far. 

The LB technique has conventionally been used to prepare monomolecular singlelayer and multi-layer films of surface active chemical species, such as phospholipids or fatty acids. Conventionally, the films are first prepared on surfaces of highly purified water, and then transferred therefrom to substrates of interest. Among common transfer techniques used are the vertical-transfer Y-Type (vertical up- and down-strokes, commonly used for hydrophobic species), X-type and Z-type (vertical up- and down-strokes only), and the horizontal-transfer lifting technique (where the surface active species simply adheres to the horizontally placed substrate). 

P(Py) to the conducting state, thus yielding alternating conducting/insulating polymer layers. 

Technique for synthesis of Langmuir Blodgett (LB) films of P(Py), after Shimidzu et al. After Reference [285], reproduced with permission. 

In a precursor-polymer synthetic approach [288], amphiphiles which formed charged complexes with precursor polymers of poly(p-phenylene vinylene) (P(PV)) and poly(thienylene vinylene) (P(TV)) were spread onto solutions of these precursor polymers. This unique complex is then transferred to an appropriate substrate using standard LB techniques, and then converted to P(PV) or P(TV) via heat treatment. In a similar but rather novel, in-situ polymerization approach from the Rubner group [289], LB films of ferric stearate are exposed sequentially to HCl vapor (generating FeCls oxidant) and pyrrole monomer, yielding conductive LB P(Py) films. 

---