Mechanochemical Processing of Highly Conducting Organic/Inorganic Composites Exhibiting Spin Crossover–Induced Memory Effect in Their Transport Properties

Bistable multifunctional materials have great potential in a large variety of devices, from sensors to information units. However, the direct exploitation of spin crossover (SCO) materials in electronic devices is limited due to their very high electrical resistance (insulators). Beyond their intrinsic properties, SCO materials may also work as probes to confer bistability as switchable components in hybrid materials, as controlled by external stimuli acting upon the SCO spin state. Low resistance conductors with memory effect may be obtained from the incorporation of SCO probes into a conducting organic polymer matrix. This strategy appeared to be limited by the strict synthetic conditions, since polymerization reactions are harsh enough to attack the redox-unstable SCO component. Because of this, just a few successful examples have been reported. Here a versatile processing protocol is introduced to obtain SCO/conducting polymer composites exploiting a post-synthetic mechanochemical approach that can be applied to any SCO component and any organic polymer. This new protocol allows highly conducting films of polypyrrole, polyaniline, and poly(3,4-ethylenedioxythiophene) (PEDOT) to be obtained, with bulk conductivities as high as 1 S·cm⁻¹, and exhibiting a thermal hysteresis in their electrical conductivity above room temperature.