The effect of UV irradiation on air/water interfacial activity of Tween 20-coumarin conjugates

초록

In order to obtain photo-sensitive surfactants, coumarin derivatives were covalently attached, through either ester bond or ether bond, to hydroxyl groups located at the ends of PEO segments of Tween 20. The molar ratios of Tween 20 to coumarin residues in both Tween 20-coumarin conjugate having ester bond (TCES) and ether bond (TCET) were about 1:1 despite the excess coumarin in the reaction mixture. The photo-dimerization degree was in the order of TCET > TCES > a free coumarin derivative. And the air/water interfacial activity was in the order of TCET > Tween 20 > TCES. The interfacial activities of TCES and TCET increased with the UV irradiation time. This is possibly because the coumarin residues of TCES and TCET are photo-dimerized to produce Gemini surfactant-like dimeric surfactants. The photo-induced change in the interfacial activity of TCES was slightly greater than that of TCET, probably due to the difference in the length, the polarity, and the flexibility of the linker between two monomeric conjugates of Gemini-like dimeric surfactants.

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