In order to evaluate the influence of plasticizers on the behavior of the dielectric properties of polymers intended for the elaboration of flexible sensors, we have studied the influence of the addition of glycerol (10 wt%–40 wt%) in polyvinyl alcohol (PVA). Once processed, the PVA films were not subjected to any particular annealing and they were dried at room temperature for 24 h before being characterized. This choice allows both to take advantage of the presence of water in the bulk of the material, which will help to make the PVA more flexible (increase of plasticization effect produced by extra-H-bonding) and avoid a transient behavior of water absorption into the material, as we could verify. DSC and FTIR investigations confirm good intermolecular interaction between vinyl polymer chains, glycerol, and water molecules. Dielectric spectroscopy analysis, carried out in [25°C–110°C] temperature and [0.1 Hz–1 MHz] frequency ranges, reveals a significant increase in the dielectric constant when the glycerol content is higher (at 0.1 Hz: 322 for pure PVA, 1.3 × 10⁶ with 40 wt% of glycerol). Polar hydrogen bonds introduced by the glycerol are the main reason for this increase. Ionic conductivity induced by these dipoles dominates the loss tangent response of the material. The activation energy obtained from the DC conductivity plateau obeys to a conventional Arrhenius law with a decreasing value at highest glycerol contents (1.35 eV for pure PVA against 0.46 eV with 40 wt% of glycerol).

中文翻译：

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甘油化氢键聚乙烯醇薄膜的结构、热和介电性能

为了评估增塑剂对用于制作柔性传感器的聚合物介电性能行为的影响，我们研究了在聚乙烯醇 (PVA) 中添加甘油 (10 wt%–40 wt%) 的影响. 加工后，PVA 薄膜不进行任何特殊退火处理，并在表征前在室温下干燥 24 小时。这种选择既可以利用大部分材料中存在的水，这将有助于使 PVA 更灵活（增加额外氢键产生的塑化效果）并避免吸水进入的瞬态行为材料，正如我们可以验证的那样。DSC 和 FTIR 研究证实了乙烯基聚合物链、甘油和水分子之间良好的分子间相互作用。⁶含 40 wt% 的甘油）。甘油引入的极性氢键是这种增加的主要原因。由这些偶极子引起的离子电导率决定了材料的损耗角正切响应。从 DC 电导率平台获得的活化能服从传统的 Arrhenius 定律，在最高甘油含量下具有递减值（纯 PVA 为 1.35 eV，而甘油含量为 40 wt% 时为 0.46 eV）。