Elsevier

European Polymer Journal

Volume 34, Issue 12, December 1998, Pages 1767-1774
European Polymer Journal

Electrochemically synthesized polypyrrole nanotubules: effects of different experimental conditions

https://doi.org/10.1016/S0014-3057(98)00034-2Get rights and content

Abstract

Nanotubules of polypyrrole (PPy) were electrochemically synthesized using the pores of nanoporous polycarbonate (PC) particle track-etched membranes (PTM) as templates. The influence of some conditions of electrosynthesis (electrochemical method, monomer concentration, electrolyte concentration and nature) on the kinetics of pyrrole electropolymerization and on the morphology of the obtained nanomaterials has been investigated. In particular, the empirical kinetics of the electrochemical generation of polypyrrole–perchlorate (PPy–ClO4) from aqueous solution, at 0.8 V (vs SCE) was followed by electrical charges measurement. The orders with respect to pyrrole and LiClO4 are 0.34 and 0.70 respectively. The electrogeneration of polypyrrole–polystyrenesulfonate (PPy–PSS) was also followed and shows that an increase of the electrolyte concentration increases the polymerization rate at constant potential. Finally, the morphology of PPy nanotubules doped with LiClO4 and NaPSS has been studied by high resolution emission SEM and by TEM.

Introduction

Currently there is a considerable interest in nanoscale materials, since they exhibit novel properties largely as a consequence of their finite small size. Moreover, nanomaterials have wide-ranging implications to a variety of areas, including chemistry, physics, electronics, optics, materials science and the biomedical sciences. A possible chemical approach for building such nanoscale objects involves the use of nanoporous host materials as templates[1]. In particular, Martin et al.2, 3 described a new method for preparing organic microtubules which consists in using a microporous membrane as a template during tubules synthesis. Until now, most of their work has focused on the synthesis of polypyrrole, poly(3-methylthiophene) and polyaniline inside the pores of a polycarbonate Nucleopore membrane. These polymers can be synthesized by oxidative polymerization of the corresponding monomer. This may be accomplished either electrochemically or with a chemical oxidizing agent. Although they reported, once on the electrochemical synthesis of pyrrole, Martin et al. essentially used the chemical way consisting in using a template membrane as a dividing wall between a solution of monomer and a ferric salt polymerization agent[4]. The monomer and oxidizing agent diffuse toward each other through the pores in the template membrane, and react to yield the polymer.

Recently, in parallel to the development of preparation process and characterization techniques of nanoporous particle track etched membranes (nano PTM)5, 6, 7, we consider the use of these nano PTM as templates for the synthesis of nanoscale polymers. We started with the electropolymerization of pyrrole inside the pores of polycarbonate (PC) nano PTM. Until now, not much attention has been paid to the study of the influence of the synthesis parameters on the electropolymerization of pyrrole in confined medium. The aim of this paper is to determine how different synthesis parameters (the applied potential, the monomer concentration, the electrolyte nature and concentration) influence the pyrrole electropolymerization process and the morphology of the obtained materials.

Section snippets

Materials

The present work was carried out in aqueous solutions. Purified water obtained by passing distilled water through a milli Q (Millipore) water purification system was used as solvent. Pyrrole (Janssen) was distilled under low pressure prior to use. The poly (sodium-4-styrenesulfonate) (NaPSS, Acros) and the lithium perchlorate (LiClO4, Aldrich) were used without any prior purification.

The microporous polycarbonate particle track-etched membranes (PTM) used in this work were obtained by the

Results and discussion

In order to investigate the influence of electrochemical synthesis parameters on the electropolymerization of pyrrole inside the pores of a PC nano PTM and on the morphology of the obtained polypyrrole nanostructures, the following initial conditions were used: polymerization potential of 0.8 V vs calomel reference electrode in a 0.1 M pyrrole aqueous solution containing 0.1 M of LiClO4. The polymerization was performed at 25°C. SEM micrographs of the template synthesized polypyrrole

Conclusion

The overall objective of this investigation was to determine the effects of different synthesis parameters (electrosynthesis method, monomer concentration, electrolyte nature and concentration) on pyrrole electropolymerization inside the pores of PC PTM and also their effects on the morphology of the nanostructures obtained.

Using a pulsed technique, in order to let monomer and electrolyte regularly diffuse inside the pores, instead of the chronoamperometry method to electrosynthesize

Acknowledgements

The authors thank the “Services Fédéraux des Affaires Scientifiques Techniques et Culturelles” for their financial support in the frame of the “Pole d'Attraction Interuniversitaires”. Thanks also go to P. Lipnik for TEM analysis.

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