抄録
The interaction between three direct dyes and four nonionic surface active agents, polyoxyethylene dodecyl ethers, was investigated by means of filter paper capillary analysis. In particular, the effect of the polyoxyethylene chain length (n=5-8) of the surfactants, the chemical constitution of the dyes, and the temperatures (10-30°C) on the interaction was studied.
The direct dyes interact with the polyoxyethylene dodecyl ethers to form complexes DSm. The stoichiometric number (m) was 1.4 to 2.0. The equilibrium constant (K) and standard affinity (-Δμ°) of the interaction increased with an increase in the temperature. K and -Δμ° increased in the order of penta-<hexa-<octa-<hepta-oxyethylene dodecyl ethers and decreased in the order of Scarlet 4BS>Orange S>Rhoduline Red B. The favorable free energy of the interaction was accompanied by a large entropy gain and an endothermic enthalpy change.
It is suggested that the interaction between the direct dyes and polyoxyethylene dodecyl ethers is appreciably affected by the polyoxyethylene chain length of the surfactants, the chemical constitution of the dyes, and the temperatures and that it is dependent on loss of icelike water structure associated with the hydrophobic groups of the dyes and the surfactants.
