Poly[oxymethylene-oligo(oxyethylene)] for use in subambient temperature electrochromic devices

Polymer electrolytes were prepared from oxymethylene-linked polyethylene glycol 200 with lithium perchlorate at O:Li mole ratios of 10, 25 and 70, and with zinc iodide at an O:Zn mole ratio of 70. At the higher salt concentrations (O:Li ≤ 25), the electrolytes were amorphous at temperatures down to −20 °C. Conductivity was measured over a range of temperatures (eg for O:Li = 25, σ ranged from 4 × 10−8 S cm−1 at −10 °C to 2 × 10−4 S cm−1 at 70 °C). A prototype electrochromic device was constructed for which the progression of a colour front was temperature dependent. Such a device could be utilized as a time-temperature integrating sensor for indicating whether frozen goods have been stored correctly.