Elsevier

Materials Research Bulletin

Volume 34, Issue 8, 8 October 1999, Pages 1187-1194
Materials Research Bulletin

Original Articles
Preparation and evaluation of composites from montmorillonite and some heterocyclic polymers: 3. a water dispersible nanocomposite from pyrrole-montmorillonite polymerization system

https://doi.org/10.1016/S0025-5408(99)00121-XGet rights and content

Abstract

Montmorillonite (MMT)-based nanocomposites of polypyrrole (PPY) were prepared through the polymerization of pyrrole with MMT and FeCl3-impregnated MMT in bulk and in aqueous medium. The composites were characterized by IR, X-ray diffraction (XRD), and scanning electron microscopy (SEM) studies. XRD analyses revealed no change in d001 spacing in MMT (9.8 Å), suggesting no intercalation of PPY into MMT lamellae. TEM analysis indicated the particle size to be 25 ± 7 nm. The bulk conductivity of the composites was in the range of (1.3 to 26) × 10−5 S/cm, depending on the FeCl3-impregnation level and on the PPY loading in the composites. Suitable procedures were developed for obtaining a stable aqueous dispersion and a reversible dispersion of these composites.

Introduction

Nanodimensional composites of polypyrrole (PPY) with colloidal silica [1], tin(IV) oxide [2], and zirconium(IV) oxide [3] have been studied extensively. Literature on montmorillonite (MMT)-based nanocomposites of heterocyclic polymers is relatively meager despite the vast work on clay polymer interaction [4]. A MMT-poly(N-vinylcarbazole) nanocomposite has recently been produced by interaction of N-vinylcarbazole with MMT [5] and FeCl3-impregnated MMT [6]. A MMT-PPY nanocomposite has been prepared by mixing a preformed PPY colloid with MMT exfoliated in water [7]. Based on this background, we have developed a simple procedure for preparing a water-dispersible PPY-MMT nanocomposite by reacting pyrrole monomer with MMT and FeCl3-impregnated MMT. This article highlights the preparation of the composites, their morphological characterization, and dc conductivity trend.

Section snippets

Polymerization and isolation of composite

PPY-MMT composites for this study were prepared through the following procedures.

  • 1.

    Pyrrole-MMT system (bulk). A known amount of vacuum-dried (100°C) powdery MMT (Aldrich) was placed in a stoppered Pyrex tube to which a known quantity of pyrrole (Aldrich) was added and the reaction mixture was stirred continuously at 50°C for 3 h.

  • 2.

    Pyrrole-FeCl3 impregnated MMT (bulk). FeCl3-impregnated MMT was prepared by a thorough mixing of an acetone solution of anhydrous FeCl3 of required concentration with

Composite formation

The addition of pyrrole monomer to the MMT was accompanied by a gradual color change of the reaction system from light gray to greenish-blue to black, indicating formation of PPY. In general, the yield of PPY formed through the direct interaction of pyrrole and MMT was about 5% in 3 h, which suggests that MMT is a very weak initiator for pyrrole polymerization, in sharp contrast to N-vinylcarbazole [5]. Table 1 presents some relevant data on the formation of PPY-MMT composites under various

Conclusions

MMT-based nanocomposites of PPY were obtained by polymerizing pyrrole in the presence of FeCl3-impregnated MMT in aqueous medium. These nanocomposites produced an aqueous dispersion stable for 40 h and a permanently stable dispersion in the presence of PVP. On adding pyrrole and FeCl3 to an aqueous dispersion of MMT in polyvinylpyrrolidone, a permanently stable dispersion of the PPY-MMT nanocomposite was obtained, which could be dried and redispersed in water repeatedly.

Acknowledgements

We thank CSIR, New Delhi, India, for funding an Emeritus Scientist Project for M.B., and the authorities of Presidency College, Calcutta, for use of its facilities.

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