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Identifier

000462693

Title

Μελέτη νανοσύνθετων υλικών με βάση το Nafion

Alternative Title

Investigation of Nafion-based nanocomposites

Author

Καδιανάκη, Αικατερίνη Γ.

Thesis advisor

Αναστασιάδης, Σπύρος

Reviewer

Χρυσοπούλου, Κυριακή
Δαλέτου, Μαρία

Abstract

Polymeric nanocomposites have attracted significant attention within the scientific community in the recent years. This increased interest is attributed to the remarkable improvements in their inherent properties compared to those of pure polymers or the corresponding composites. In this work, nanohybrids were developed utilizing Nafion as the main polymer; this polymer is well known for its applications in selectively permeable membranes or as electrolyte in electrolysis for high-purity H₂ production. Alternatively, poly(ethylene oxide), PEO, which is widely used polymer was utilized as well. Two different clay minerals of different morphology, halloysite and sodium montmorillonite were used for the development of the hybrids. In the first part of the study, nanocomposites were prepared utilizing two different Nafion polymers, one in an aqueous dispersion (Nafion D1021) and one in a dispersion of water/isopropanol mixture (Nafion D2021), together with different halloysites. The nanorods of halloysite were used either unmodified or modified using cold plasma reactors (O₂ and Argon) during various processing times, as well as through chemical modification using covalent bonds to enhance the interactions with the polymer. Different compositions of nanocomposites were fabricated and all materials were characterized for their thermal stability and structure using Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). In all cases, a large part of halloysite sediments in the dispersion and the remaining is not sufficiently dispersed within the polymer matrix. The results were very similar results in the cases of both the natural and the surface modified ones, whose additional groups were not capable of improving the dispersion and the interaction of halloysite with Nafion. In the second part of this study, nanocomposites were synthesized utilizing Nafion and montmorillonite, as well as PEO and modified and unmodified halloysite, to investigate their dispersion and their thermal stability and compare them with the ones of the first part. These nanocomposites were studied and characterized using the previously mentioned techniques; in the case of PEO nanocomposites the polymer crystallization was investigated via Differential Scanning Calorimetry (DSC). As far the system with montmorillonite is concerned, the importance of the different pH between its aqueous dispersion and the dispersion of Nafion was found to be the main reason preventing the formation of stable dispersions. On the other hand, for the nanocomposites with PEO, it was observed that more favorable interactions exist between the polymer and halloysite, as indicated by the quantities of the clay remaining both in the dispersion and in the final nanocomposites.

Language

Greek

Subject

Composition

Halloysite

Montmorillonite

PEO

Polymer nanocomposite materials

Silicate minerals

Structure

Αλλοϋσίτης

Δομή