Tunable mechanical properties of [Fe(pyrazine){Au(CN)2}2]–PVDF composite films with spin transitions

Here we describe the elaboration and investigation of composites prepared from the spin-crossover (SCO) complex [Fe(pyrazine){Au(CN)2}2] and poly(vinylidene fluoride) matrix, with different contents of the active phase (10–35 wt%). Optical measurements demonstrated that all composites preserve temperature induced hysteretic spin transitions. Tensile mechanical analysis showed a non-linear change of the Young's modulus upon increase of the complex content. Thermomechanical analysis upon a constant strain demonstrated pronouncable alterations of the applied stress in the SCO region. Composites with smaller loads require less stress to attain a given strain in the high-spin state, however for those with high loads the behaviour is more sophisticated. The modelling of stress vs. temperature behaviour revealed that this may be interpreted through a miscellaneous interplay of expansion of both the polymer and the complex, the contribution of both components to the elastic properties of composites, and the effects of SCO on these properties.