Role of salt concentration on conductivity optimization and structural phase separation in a solid polymer electrolyte based on PMMA-LiClO4

Abstract

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.

Enhancement in electrical and stability properties of amorphous polymer based nanocomposite electrolyte

“…Of these possibilities, the cation has a tendency to coordinate with the C Ö site of the PMMA due to its stronger electron donicity than O-CH 3 . This possibility has also been confirmed in the FTIR spectrum results as reported by us [20] previously. Hence, the C Ö is the only site in the backbone of PMMA monomer units where Li + coordinate (Fig.…”

“…These changes observed in terms of broadening and asymmetry of υ(C Ö) band of PMMA provide strong and convincing evidence for polymer-ion interaction in the PS film possibly due to cation coordination at C Ö site of the polymer chain. This feasibility of columbic interaction between the cation and electron rich site (C Ö) of PMMA due to strong polymer-ion interaction appears to be consistent with our previous report [20]. Fig.…”

Ionic conductivity and relaxation studies in PVDF-HFP:PMMA-based gel polymer blend electrolyte with LiClO4salt

“…This indicates the strong interaction of Li ions with the carbonyl group of PMMA. Similar observations were also reported by Shukla et al 23 in their FTIR studies of lithium salt polymer complexes. Apart from this, the peak at 2950 cm À1 ascribed to CH 3 asymmetric stretching is shifted to 2954 cm À1 in the complexes.…”

Effect of melt compounding temperature on dielectric relaxation and ionic conduction in PEO–NaClO4–MMT nanocomposite electrolytes

“…Recently, there has been an increasing interest to develop the novel solid polymer electrolytes and montmorillonite (MMT) clay added polymer nanocomposite electrolytes (PNCEs) of improved mechanical, thermochemical, electrochemical, and structural stability properties for their technological applications [1][2][3][4][5]. The main factor that rules the ionic conductivity of PNCEs is to suppress the crystallinity of the polymer and ion pair formation (anion complex cation interactions) besides the increase of the number of charge carriers [3][4][5][6][7][8][9].…”

“…The main factor that rules the ionic conductivity of PNCEs is to suppress the crystallinity of the polymer and ion pair formation (anion complex cation interactions) besides the increase of the number of charge carriers [3][4][5][6][7][8][9]. Earlier X-ray diffraction (XRD) and morphological studies [4][5][6][7][8][9] established that the addition of intercalated and exfoliated structures of MMT clay in PNCEs impede the polymer crystallization, which increases their ionic conductivity.…”