The poly(ethylene terephthalate)/polyaniline composite: AFM, DRS and EPR investigations of some doping effects

A composite based on PET as a matrix and a thin layer of PANI produced by c hemical polymerisation of aniline in the surface layer of the PET is invest igated by means of four probe conductivity method, standard and conducting AFM, DRS and EPR techniques. Conducting AFM shows that PANI forms conductin g clusters. Standard AFM topographical images prove that the undoped form o f the composite has a flat surface, whereas the doped one exhibits mountain ous features. DRS spectra revealed that the transition from the undoped for m to the doped one is accompanied with an increase of the high frequency pe ak associated to conductivity of the clusters leading to the appearance of two low frequency relaxation processes connected with interfacial polarizat ion phenomena. It is found that the relaxation behaviors of the composite d oped by HClO4 and HCl acids are similar. The EPR spectra obtained in both d oped and undoped forms of the composite are induced by two kinds of paramag netic centres (PC). Irrespective to the dopant, anomalous thermal behaviors of the PC spin relaxation times and susceptibilities are evidenced above 1 80 K. These effects are connected with changes in the electronic transport properties. (C) 2001 Kluwer Academic Publishers.