Quantitative analysis of surface morphology: characterization of polypyrrole films aging

The structure and properties of polypyrrole have been studied intensively i n the past decade. Polypyrrole microstructure and morphology are quite well described, nevertheless they remain roughly characterized from a quantitat ive point of view. In a previous work, one of the authors has underlined ch anges in some physical and microstructural properties which are linked to m olecular mobility but the influence of aging on morphology has not been stu died. To fill this gap, SEM and AFM observations have been performed. The s urface morphology of polypyrrole films looks like 'cauliflowers' that are m ade of clusters aggregated on a large range of scales. Fractal methods have been used to treat quantitatively the pictures: the fractal dimension D (e stimated from Minkowski) has a tendency to decrease for the aged material v iewed by SEM as well as by AFM. Pseudo Fractality Graphs (the variation of D along the scales) show that the difference between virgin and aged polypy rrole is higher for the largest scales. The topography analysis is compared by using AFM and SEM pictures. (C) 1999 Elsevier Science Ltd. All rights r eserved.