Although a large number of ionic conductors based on poly(methyl-methacrylate) (PMMA) are reported in literature, an optimization of salt concentration with respect to conductivity and stability properties remains by and large neglected. We report, perhaps for the first time, such an optimization of salt (LiClO 4 ) concentration on structural, morphological, electrical, and ion-polymer interaction in PMMA-based solid polymer films. The active coordination site for the cation (Li + ), out of the two possible electron donating functional groups (i.e. C=Ö and Ö-CH 3 ) in PMMA, has been ascertained on the basis of evidences recorded in Fourier transform infrared spectrum. The results suggested C=Ö as the only possible site in PMMA matrix for coordination with Li + cation. The X-ray diffraction results have clearly indicated an optimum limit of salt dissolution in PMMA matrix corresponding to O/Li = 4 (i.e.,~21wt.%) above which "phase-separation" occurs distinctly. The effect of salt concentration on amorphous → crystalline phase changes in PMMA and its correlation to morphology have been clearly observed in terms of their impact on electrical properties. An optimum electrical conductivity of~7.2 × 10 −5 S cm −1 has been recorded at 100°C (~PMMA glass transition). The temperature dependence of conductivity follows typical VogelTamman-Fulcher behavior.

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A new combination of ionically conducting polymer-clay nanocomposites based on (PAN) 8 LiClO 4 þ x wt % montmorillonite (unmodified) clay has been prepared using the standard solution cast process. X-Ray diffraction (XRD) analysis reveals strong interaction of polymer salt complex (PS) with the montmorillonite matrix evidenced by changes in d 001 spacing of the clay and enhancement in the clay gallery width on composite formation possibly due to intercalation of polymer-salt complex into nanometric clay galleries. Evidences of such an interaction among polymer-ion-clay components of the composite matrix has also been observed in the Fourier transform infrared (FTIR) spectrum results. FTIR results clearly indicated cation (Li þ ) coordination at nitrile (CBN) site of the polymer backbone along with appearance of a shoulder suggesting strong evidence of polymer-ion interaction. Addition of clay into the PS matrix has been observed to affect ion-ion interaction resulting from ion dissociation effect at low clay loading in the PNC films. Complex impedance spectroscopy (CIS) analysis has provided a response comprising of a semicircular arc followed by a spike attributed respectively, to the bulk conduction and electrode polarization at the interfaces. Electrical transport appears to be predominantly ionic (t ion ¼ 0.99) with significant improvement in the electrical conductivity and thermal stability properties. Figure 10. Complex impedance spectrum (CIS) of PNC films [(PAN) 8 LiClO 4 þ x wt % Montmorillonite (MMT)] of different clay concentration at room temperature.

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