The effect of titanium dioxide nano-filler on the conductivity, morphology and thermal stability of poly(methyl methacrylate)—poly(styrene-co-acrylonitrile) based composite solid polymer electrolytes

The composite solid polymer electrolyte (CSPE) samples, comprising of poly(methylmethacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN)/ethylene carbonate (EC)/propylene carbonate (PC)/lithium trifluoromethanesulfonate (LiCF₃SO₃)/anatase-TiO₂ as nano-filler (0, 5, 6, 7, 8 and 9 wt% for samples T0, T1, T2, T3, T4 and T5 respectively) were prepared by solution casting technique. Fourier transform infrared (FT-IR) spectral studies indicate the interaction of PMMA and plasticizers (EC, PC) with Lithium ion and nano-filler TiO₂ in samples. From AC impedance studies ionic conductivity, dielectric constant increase with increase in the concentration of nano-filler TiO₂ up to 9 wt%. The sample T5 shows lowest activation energy (E_a) of 0.14 eV, very short relaxation time (τ) of 1.49 × 10⁻⁷ s and exhibits maximum ionic conductivity of 1.05 × 10⁻⁴ S cm⁻¹ at room temperature. The conductivity-temperature dependence studies showed that the conductivity of all samples depict Arrhenius behaviour suggesting ion-hopping mechanism. Dielectric studies reveal ion conducting nature of CSPE samples. Thermogravimetric analysis indicate the thermal stability of CSPE sample T5 up to 333 °C with maximum degradation at 388 °C. DSC studies reveal absence of glass transition temperature (T_g) of atactic component of PMMA in CSPE sample T5 indicating amorphous nature. X-ray diffraction patterns shows shift in the position of peaks confirming the complex formation of the PMMA-SAN-EC-PC-LiCF₃SO₃-TiO₂ system. SEM analysis indicates that the presence of lithium salt and filler TiO₂ on polymer host does not lead to heterogenous polymer blend thus retaining its amorphous nature.