Smart Coatings: Nanostructured Conjugated Polymer Network Ultrathin Film Using the Precursor Polymer Approach

By Rigoberto Advincula

The coatings industry has had a fascination with “smart coatings” fm some time. Smart coatings are not new in the sense that they take into ac­count everyday applications using new materials and mechanisms to im­prove the performance of existing coatings. On the other hand, because of fundamental discoveries made in the field of polymeric and inorganic mate­rials there is a potential to generate new and “smart applications.” The use of so-called macromolecular assemblies in ultrathin films provides new ways of assembly of ultrathin film coatings even through a layer-by-layer approach.

Organic n-conjugated polymers and intrinsically conducting polymers(ICPs) have shown very promising behavior as alternative electrical conduct­ing, nonlinear optical, and electroluminescent materials. 1 Other applications include: energy storage, electrochromic displays, sensors, charge-dissipation, and anticorrosion coatings. Both doped and undoped forms are being inves­tigated for these applications with the idea of replacing their inorganic mate­rial counterpart. A wealth of synthetic techniques leading to novel molecular, macromolecular, and microstructural design has been reported.

Electrochemical methods have been utilized to control the oxidation poten­tial for polymerization and investigate the resulting electronic properties of these polymers. In this case, the conjugated polymers are formed in-situ as the monomers are polymerized (radical cation mechanism) and deposited on a conductive electrode. Recently, the importance of optical film qualities of these materials has been emphasized for electrochromic applications. For non-doped film applications such as polymer light-emitting diode (PLED) and field effect transistor (FET) devices, the optical dielectric constants, charge carrier properties, thickness, morphology ( crystallinity or aggrega­tion), and layer order of the films are deemed to be important.