Thermochromic properties of nano- and microcomposites based on (NH2(C2H5)2)2CuCl4 crystals

The absorption spectra of [NH2(C2H5)2]2CuCl4 (DEACC) nanocrystals and microcrystals incorporated into the polymer matrices were investigated.The main attention was devoted to the size eects manifestation in the spectral properties of the nano-and microcomposites based on DEACC crystals.It has been found that contrary to the case of the initial bulk crystals undergoing the rst order thermochromic phase transition, the composites with the nanocrystals of average size 160 nm are characterized only by continuous change of color.Polymer-based microcomposites with an average microcrystal size of 20 µm were found to possess the thermochromic properties similar to those in a bulk crystal, although their discontinuous thermochromic phase transition was shifted to higher temperatures (316 K) compared to the case of the bulk crystal (311 K).Besides, these microcomposites are characterized by a more diused hysteresis loop observed on the temperature dependence of the absorption coecient at the constant wavelength reecting the hysteresis of the phase transition temperature.The signicant eect of the polymer matrix on the phase transition temperature and nature was also detected.Indeed, the polysterene-based microcomposites with an average microcrystal size of 200 µm were found to possess the thermochromic properties similar to those in a bulk crystal, although their discontinuous thermochromic phase transition was more considerably shifted toward higher temperatures (337 K) compared to the case of the bulk crystal.It was suggested that the rigid polystyrene matrix more signicantly aects the geometry of the anionic [CuCl4]2-complex than the softer latex matrix.