The formation of a coloured complex of partially saponified poly(vinyl acetate) with iodine in the presence of potassium iodide

The red‐violet complex which was formed from partially saponified poly(vinyl acetate) and iodine in the presence of potassium iodide was investigated by the Benesi‐Hildebrand method. The molar absorption coefficient of the complex at the absorption maximum (488 nm) was found to be 4,74.1041/(mol cm) at 10°C and to decrease with rising temperature. The concentration of units resulting from vinyl acetate (acetoxyethylene units), which can take part in the complex formation with iodine, was below 1% of the total content of acetoxyethylene units in the polymer. The changes of enthalpy (ΔH) and entropy (ΔS) were found to be −45,01 kJ mol−1 (−10,75 Kcal/mol) and −48,40 J mol−1 K−1 (−11.56 cal mol−1 K−1) at 15°C, respectively.