The two previous sections have focused exclusively on the most general structural properties that occur as a natural consequence of conducting polymer synthesis and the subsequent treatments of bulk samples. In fact there are a variety of even more evolved conducting polymer structures that may be generated through highly specialized processing and/or synthesis procedures. This section will briefly discuss only one of the many possible novel structural architectures that have been envisioned.
Langmuir-Blodgett (LB) monolayer films deposition techniques have been employed for many years in the fabrication of multilayer thin film structures. The basic technique involves the preparation of various monolayer films at an air-liquid interface and the subsequent step-wise transfer of these monolayers to an appropriate substrate thereby building up a supermolecular assembly. Typically chemical compounds incorporating hydrophilic and hydrophobic moeties are used to stabilize the monolayers on an aqueous subphase. To enable the incorporation of conducting polymer hosts into the production of these LB multilayer assemblies a number of reaction and processing schemes have been employed. These include the direct manipulation of soluble surface active derivatives, the transfer of various surface active monomers followed by a secondary polymerization of the multilayer films and, finally, the incorporation of various mixed phases which contain both conducting polymers and conventional LB agents (e.g., steric acid) agents.
Alternatives to LB techniques for the preparation of multilayer thin films are also available. Control of the microscopic ordering can be achieved through structured self-assembly methods. Lamellar conjugated polymer structures have been prepared using in situ electrochemical polymerization of heteroarene-containing surfactants from micellar solutions. This method avoids the highly controlled conditions necessary for monolayer film formation.
The resulting multilayer films can exhibit extremely high degrees of structural ordering and anisotropy. Diffraction studies of these films typically exhibit a series of evenly spaced low angle reflections in analogy to the lamellar phases of the P3AT's discussed in the previous section. Unlike the P3AT's, these layers are highly parallel to the substrate. The in-plane anisotropy is, at preset, more difficult to control and the full set of details concerning the structural ordering and structure/property interrelationships are still incomplete.