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<p>This work investigates the impact of doping and temperature on the dielectric properties of polyvinyl chloride (PVC)/polyethylene glycol (PEG) blended with ZnCo<sub>1.8</sub>Al<sub>0.2</sub>O<sub>4</sub>, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and tetrahexylammonium iodide (THAI) or energy storage applications requiring high dielectric performance. The composite films were fabricated using casting and hydrothermal methods. The effects of the dopants on the structure and morphology of the host polymer were examined. XRD analysis revealed that the crystallinity index decreased from ~ 35–40% for the pure PVC/PEG blend to ~ 25–30% upon filler incorporation, indicating disruption of polymer chain ordering. The influence of frequency (10<sup>2</sup>–10<sup>6</sup> Hz) and temperature (293–353 K) on the dielectric properties was systematically analyzed. The real part of the dielectric constant (ε′) at 10<sup>2</sup> Hz increased from ~ 8 for the pure blend to ~ 80 for the composite containing 3 wt% THAI, while the sample with undoped sample exhibited the lowest dielectric loss (<i>ε</i>′′ ≈ 12 at 10<sup>2</sup> Hz). AC conductivity (σₐ<sub>c</sub>) at 10<sup>6</sup> Hz showed a temperature-activated increase from ~ 10⁻<sup>6</sup> S/cm at 293 K to ~ 10⁻<sup>4</sup> S/cm at 353 K for the optimally doped sample (4 wt% THAI). Nyquist plot analysis revealed that bulk resistance decreased dramatically from 4.4 × 10<sup>16</sup> Ω for the undoped blend to 2.0 × 10<sup>8</sup> Ω upon ZnCo<sub>1.8</sub>Al<sub>0.2</sub>O<sub>4</sub> addition, confirming its role as a conductivity booster. The frequency exponent (<i>s</i>) decreased from 0.85 to 0.60 with increasing temperature for filled samples, indicating a correlated barrier hopping (CBH) conduction mechanism, while the undoped blend followed the quantum mechanical tunneling (QMT) model with temperature-independent <i>s</i> ≈ 0.75. Energy density (<i>U</i>) at 10<sup>2</sup> Hz improved from 0.5 J/cm<sup>3</sup> for the pure blend to 3.3 J/cm<sup>3</sup> for the composite with ZnCo<sub>1.8</sub>Al<sub>0.2</sub>O<sub>4</sub>/LiTFSI. These results, which for the first time elucidate the temperature-dependent conduction mechanisms and impedance characteristics of this multicomponent system, establish that the formed nanocomposites, particularly at optimal THAI loading (4 wt%), display superior dielectric features suitable for high-performance energy storage applications requiring thermal stability.</p>

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Temperature dependence of the dielectric features of PVC/PEG/ZnCo1.8Al0.2O4/LiTFSI/THAI blended polymers

  • 期刊论文

  • 发表日期：

    2026年4月6日

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  • Ahmad A. Alsaleh,
  • A. M. El-naggar

摘要

This work investigates the impact of doping and temperature on the dielectric properties of polyvinyl chloride (PVC)/polyethylene glycol (PEG) blended with ZnCo1.8Al0.2O4, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and tetrahexylammonium iodide (THAI) or energy storage applications requiring high dielectric performance. The composite films were fabricated using casting and hydrothermal methods. The effects of the dopants on the structure and morphology of the host polymer were examined. XRD analysis revealed that the crystallinity index decreased from ~ 35–40% for the pure PVC/PEG blend to ~ 25–30% upon filler incorporation, indicating disruption of polymer chain ordering. The influence of frequency (102–106 Hz) and temperature (293–353 K) on the dielectric properties was systematically analyzed. The real part of the dielectric constant (ε′) at 102 Hz increased from ~ 8 for the pure blend to ~ 80 for the composite containing 3 wt% THAI, while the sample with undoped sample exhibited the lowest dielectric loss (ε′′ ≈ 12 at 102 Hz). AC conductivity (σₐc) at 106 Hz showed a temperature-activated increase from ~ 10⁻6 S/cm at 293 K to ~ 10⁻4 S/cm at 353 K for the optimally doped sample (4 wt% THAI). Nyquist plot analysis revealed that bulk resistance decreased dramatically from 4.4 × 1016 Ω for the undoped blend to 2.0 × 108 Ω upon ZnCo1.8Al0.2O4 addition, confirming its role as a conductivity booster. The frequency exponent (s) decreased from 0.85 to 0.60 with increasing temperature for filled samples, indicating a correlated barrier hopping (CBH) conduction mechanism, while the undoped blend followed the quantum mechanical tunneling (QMT) model with temperature-independent s ≈ 0.75. Energy density (U) at 102 Hz improved from 0.5 J/cm3 for the pure blend to 3.3 J/cm3 for the composite with ZnCo1.8Al0.2O4/LiTFSI. These results, which for the first time elucidate the temperature-dependent conduction mechanisms and impedance characteristics of this multicomponent system, establish that the formed nanocomposites, particularly at optimal THAI loading (4 wt%), display superior dielectric features suitable for high-performance energy storage applications requiring thermal stability.