Polyethylene oxide-mcm-41 and polyaniline-mcm-41 nanocomposites: physicochemical and conducting properties

Abstract

One of the exciting developments in material science today is the design and synthesis of polymer nanocomposites (PNC) containing electrically-conductive polymer and mesoporous MCM-41 that possess novel properties not exhibited by the individual organic and inorganic materials. The physicochemical and conducting properties of two types of PNC namely, PEO/Li-MCM-41 and PANI/MCM-41 prepared by melt and solution intercalation and in situ polymerisation methods have been investigated in this thesis. The aim was to obtain a more detailed understanding of how the combination of polymers with the mesoporous MCM-41 is related to the conducting properties of the PNC. Before PEO and PANI are combined with MCM-41, several modifications of MCM-41 have been done including ion exchange of MCM-41 with lithium chloride, silylation of MCM- 41 with trimethylchlorosilane (TMCS) and functionalization of MCM-41 with sulfonic acid. The PNC obtained was characterized by X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric analysis and chemical analysis, followed by 27Al, 7Li and 13C/CP MAS NMR spectroscopy. It is confirmed that the structure of MCM-41 remains intact after combining with the polymers. The results from the conductivity study have proven that the PNC possesses electrical properties. It is revealed that the conductivity of PANI/MCM-41 is very much higher than PEO/Li-MCM-41 since PANI is a conducting polymer whereas PEO is a polymer electrolyte. The combination of PEO and MCM-41 was expected to increase the conductivity of PEO/Li-MCM-41 by intercalation of PEO inside the pores of MCM-41. However, it is demonstrated that unmodified Li-MCM-41 exhibits conductivity in the same order of magnitude as the PEO/Li-MCM-41. The NMR results suggested that the interfacial interactions occurring between the PEO and Li-Al-MCM-41 is insufficient to improve the conductivity of the PEO/Li-MCM-41 nanocomposite. On the other hand, PANI/MCM-41 nanocomposite shows an increase in thermal stability of conductivity compared to PANI, although its conductivity was lower in the presence of MCM-41.