Department of Biology and Chemistry, Universidad de Sucre, Sincelejo 700001, Colombia.
Faculty of Engineering and Basic Sciences, Fundación Universitaria Los Libertadores, Bogotá 111221, Colombia.
Int J Mol Sci. 2024 Aug 2;25(15):8450. doi: 10.3390/ijms25158450.
Cassava starch solid biopolymer electrolyte (SBPE) films were prepared by a thermochemical method with different concentrations of lithium triflate (LiTFT) as a dopant salt. The process began with dispersing cassava starch in water, followed by heating to facilitate gelatinization; subsequently, plasticizers and LiTFT were added at differing concentrations. The infrared spectroscopy analysis (FTIR-ATR) showed variations in the wavenumber of some characteristic bands of starch, thus evidencing the interaction between the LiTFT salt and biopolymeric matrix. The short-range crystallinity index, determined by the ratio of COH to COC bands, exhibited the highest crystallinity in the salt-free SBPEs and the lowest in the SBPEs with a concentration ratio (Xm) of 0.17. The thermogravimetric analysis demonstrated that the salt addition increased the dehydration process temperature by 5 °C. Additionally, the thermal decomposition processes were shown at lower temperatures after the addition of the LiTFT salt into the SBPEs. The differential scanning calorimetry showed that the addition of the salt affected the endothermic process related to the degradation of the packing of the starch molecules, which occurred at 70 °C in the salt-free SBPEs and at lower temperatures (2 or 3 °C less) in the films that contained the LiTFT salt at different concentrations. The cyclic voltammetry analysis of the SBPE films identified the redox processes of the glucose units in all the samples, with observed differences in peak potentials (Ep) and peak currents (Ip) across various salt concentrations. Electrochemical impedance spectroscopy was used to establish the equivalent circuit model Rf-(Cdl/(Rct-(CPE/Rre))) and determine the electrochemical parameters, revealing a higher conduction value of 2.72 × 10 S cm for the SBPEs with Xm = 17 and a lower conduction of 5.80 × 10 S cm in the salt-free SBPEs. It was concluded that the concentration of LiTFT salt in the cassava starch SBPE films influences their morphology and slightly reduces their thermal stability. Furthermore, the electrochemical behavior is affected in terms of variations in the redox potentials of the glucose units of the biopolymer and in their ionic conductivity.
木薯淀粉固态生物聚合物电解质 (SBPE) 薄膜通过热化学方法制备，其中不同浓度的三氟甲磺酸锂 (LiTFT) 用作掺杂盐。该过程始于将木薯淀粉分散在水中，然后加热以促进糊化；随后，以不同浓度加入增塑剂和 LiTFT。红外光谱分析 (FTIR-ATR) 显示了淀粉某些特征带的波数变化，从而证明了 LiTFT 盐与生物聚合物基质之间的相互作用。通过 COH 与 COC 带的比值确定的短程结晶度指数表明，在无盐 SBPEs 中结晶度最高，在浓度比 (Xm) 为 0.17 的 SBPEs 中结晶度最低。热重分析表明，盐的加入使脱水过程的温度升高了 5°C。此外，在将 LiTFT 盐加入到 SBPEs 后，热分解过程在较低温度下进行。差示扫描量热法表明，盐的加入影响了与淀粉分子堆积降解相关的吸热过程，在无盐 SBPEs 中该过程在 70°C 发生，而在含有不同浓度 LiTFT 盐的薄膜中该过程在较低温度（低 2 或 3°C）下发生。SBPE 薄膜的循环伏安分析确定了所有样品中葡萄糖单元的氧化还原过程，观察到不同盐浓度下的峰电位 (Ep) 和峰电流 (Ip) 存在差异。电化学阻抗谱用于建立等效电路模型 Rf-(Cdl/(Rct-(CPE/Rre))) 并确定电化学参数，结果表明 Xm = 17 的 SBPEs 的传导值较高，为 2.72 × 10 S cm，而无盐 SBPEs 的传导值较低，为 5.80 × 10 S cm。研究结果表明，LiTFT 盐在木薯淀粉 SBPE 薄膜中的浓度会影响其形态，并略微降低其热稳定性。此外，生物聚合物中葡萄糖单元的氧化还原电位及其离子电导率的变化会影响电化学行为。
