| Summary: | 博士 === 國立交通大學 === 應用化學系 === 90 === The objective of this study is to investigate the effect of the montmorillonite on the ionic conductivity behavior. The result has demonstrated that the addition of optimum content of the organo-modified montmorillonite (oClay) is able to enhance the ionic conductivity drastically. Specific interactions among silicate layer, ethyl oxide and lithium cation have been investigated using alternating current impedance (a.c. Impedance), differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR), and Solid-state NMR. The specific interaction is attributed to the Lewis acid-base interaction. These negative charges on the silicate layers can play the same role as the polar functional group in polymer (Lewis base) to interact with lithium cations. In the chapter 4, PEO/LiTf/Clay system, the presence of the oClay tends to influence the complex form by drawing lithium cations away from the original polymer matrix into the silicate layers’ region. The shift of the complex form will also accompany with the higher chain flexibility, different melting point (Tm), and crystallinity (Xc%). Additionally, the results of chapter 5 reveal that the presence of the oClay in the PAN/LiTf/Clay system can also increase the system’s dipolar property, and results in the lithium salts more easily dissociated.
In order to further understand the effect of intercalated property of polymer/oClay on the ionic conductivity. A model system based on poly(ethylene oxide) (PEO) doped with LiClO4 and incorporated with different oClay is investigated in the chapter 6. Although the strong interactions occur between the silicate layer and the dopant salt LiClO4 within the PEO/clay/LiClO4 system, however, the strength of this specific interaction depends on the extent of PEO intercalation. In the exfoliated clay system, (PEO)8LiClO4/DDAC-oClay, great numbers of the negative charges in the silicate layers can be dispersed homogeneously in the polymer matrix, huge numbers of negative charges on the silicate layers can interact with the lithium cation and results in the high ionic conductivity. When the DDAC-mClay = 2.9 wt%, the (PEO)8LiClO4/DDAC-oClay polymer film not only possesses the highest ionic conductivity (8×10-5 S/cm) but also maintains the excellent dimensionally stability.
In order to achieve the commercial purpose, study on the effect of adding specific amount of ethylene carbonate (EC) to the P(MMA)8LiClO4/Dclay system has also been carried out in the chapter 7. This study has demonstrated that the addition of an optimum content (5 wt%) of the oClay increases the ionic conductivity of the PMMA-based electrolyte by nearly forty times (6×10-4 S/cm) relative to the plain P(MMA)8LiClO4(25)/EC(75) system. These novel plasticized nanocomposite films not only give significantly higher conductivity but also possess improved dimensional stability for potential commercial applications. Adding clay not only enhances the ionic conductivity, but also sustains the mechanical property of the electrolytes.
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