An oligomer type surfactant was prepared by cooligomerization of acrylic acid, acrylonitrile and 1-dodecanethiol, followed by neutralization with KOH. The chemical structure of the oligomer was established by elemental analysis and IR spectrum as follows;
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The cmc of the oligomer was 0.24g/100ml and the surface tension at the cmc was about 25dyn/cm at 25.0°C. The curves of surface tension against the oligomer concentration on the addition of HCl was divided into three regions. The surface tension in the presence of KOH, KCl or CaCl
2 was also measured. The cmc was increased by the addition of KOH and lowered by the addition of KCl or CaCl
2. The lowering degree of the cmc by the addition of CaCl
2 was greater than that by KCl. The results may be attributed to the change of dissociation of ionized groups in the oligomer molecule by the additives.
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