Preparation and characterization of low environmental humidity sensitive ionic liquid polymer electrolytes

Abstract

ABSTRACTMethyl 3‐(3‐(2‐hydroxyethyl)imidazole‐1‐yl)propanoate chloride salt (IL‐Cl), methyl 3‐(3‐(2‐hydroxyethyl)imidazole‐1‐yl)propanoate bromate salt (IL‐Br), and their derivatives modified by polyethylene glycol (PEG) through ester‐exchange reaction (IL‐PEGs) were synthesized. First, the properties of those materials, especially their conductivity, have been extensively studied. Second, using the IL‐PEG with the highest conductivity as a plasticizer and electrolyte, a series of gel polymer electrolytes were successfully fabricated from polyurethane, poly‐1,4‐butylene adipate glycol 2000, and IL‐PEGs by melting blends with different mass ratios in a Haake torque rheometer. The surface morphology, thermal properties, and the surface resistivity of gel polymer electrolytes were studied by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and surface resistivity test, respectively. Scanning electron microscopy pictures showed that the surface of polymer electrolyte is smoother than that without added IL‐PEGs. Thermogravimetric analysis results revealed that the polymer electrolytes will not decompose when the processing temperature is below 275°C. It was found that the surface resistivity of polymer electrolytes can be below 109 Ω, showing a good antistatic property, and it changes slightly as the relative humidity decreases from 40% to 0.1%, indicting that the material has low humidity sensitivity. This study is a new demonstration and development in ionic liquid based polymer electrolyte. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40675.