Thermochromism methanol

Within certain restrictions, unsaturated polyester resins are made thermochromic by the addition of a methanolic Co(II) chloride solution. The unsaturated ester, CoCl2 solution, peroxide catalyst, and accelerator are combined, and the resulting composition is cured at low temperature. The cured resin is colorless at 10°C but deepens in color as the temperature rises, until a blue color is attained at 40° C. This color change is reversible however, the thermochromism is destroyed by heating to temperatures above 70°C [51]. 

Diffraction data for the alkoxy-substituted materials are scarce. For PMEEMT x-ray diffraction patterns were recorded [44] at two temperatures, room temperature and 150°C, showing in both cases three to four rather broad peaks on a diffuse background. The peaks correspond to interplanar distance d= 17.8 A, 7.0 A, 3.8 A and 2.4 A, the latter two being close to two values also found for PATs as the 6-axis parameter and a diffuse feature at 0 = 2.6 A related to the main chain periodicity. It is remarkable that the diffraction pattern survives heating to 150"C, which is above the thermochromic transition for PMEEMT. A recent diffraction study of poly methanol-thiophene) prepared electrochemically showed only broad amorphous scattering around 0= 1.4 A [94],... 

Influence of the solvent. At a given temperature, the color of the solution depends on the donor properties of the solvent S. Good donors favor the green complex ion, while the red complex is favored by the poor donors. Thermochromism is observed most readily in solvents that are intermediate donors, such as nitriles, ketones and alcohols. Mixtures of a good and a weak donor can also lead to thermochromic behavior. The binary mixtures, nitromethane/ n-butanol (70/30 mol/mol) and isoamyl alcohol/tetrachloroethane (50/50 mol/mol) have been used. Thermochromism is also observed in azeotropic mixtures such as chloroform/methanol and chloroform/ethanol. In these cases, the proportions of the two components do not require adjustment. 

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