Scratching the surface of intelligent materials: characterisation methods for conducting polymer films
One essential aspect of an intelligent material is that it has some properties which are dynamic which can be utilised and controlled. It is well known that a number of polymeric materials are inherently dynamic. In order to utilise the full potential of polymers for use as intelligent materials it is imperative that processes occurring at the polymer interface are well understood. A large range of surface and other techniques are available to characterise this. At IPRL we has developed over a number of years intelligent material systems based on conducting polymers such as polypyrrole. This range of materials has been used as coated films, particles or stand-alone membranes in systems designed either to sense/monitor the environment or to effect a separation. Polypyrrole based systems are able to perform sophisticated functions because the polymer is a dynamic material which can change its chemical and physical properties by application of an electrical potential (thereby altering the oxidation state of the polymer). This change is accompanied by movement of ions in and out of the material. The paper presents results for a number of characterisation techniques which elucidate what is happening at the polymer-solution interface such as cyclic voltametry and quartz crystal microbalance, together with other surface techniques such as scanning electron microscopy and the atomic force microscope which provide a microscopic picture of the polymer surface. It is shown that only by using a wide range of techniques is it possible to gain a full understanding of the unique properties of intelligent material such as polypyrrole. Only then can it be said that one is truly more than just scratching the surface.