Materials with a positive temperature coefficient have many applications, including
overcharge and over-temperature protection in lithium-ion (Li-ion) batteries. The thermoresistive
properties of an electrically conductive polymer, based on a Ni(salen)-type backbone, known as
polyNiMeOSalen, were evaluated by means of in situ resistivity measurements. It was found that the
polymer was conductive at temperatures below 220 ◦C; however, the polymer increased in resistivity
by three orders of magnitude upon reaching 250 ◦C. Thermogravimetric results combined with
elemental analyses revealed that the switch from the insulation stage to the conductive stage resulted
from thermally dedoping the polymer. Electrochemical studies demonstrated that a polymer retains
its electroactivity when it is heated and can be recovered to a conductive state through oxidation via
electrochemical doping in an electrolyte solution.