The CMCs, γcmcS and micropolarities of aqueous solutions of sodium undecenoate(UNDE) and sodium undecanoate (UNDA) have been studied by surface tension measurement and fluorescence method. It is revealed that double bond at the en of hydrophobic chain weakens its hydrophobicity, hence lowering the effectiveness of micelle formation and that of surface tension reduction. The limited adsorption amount is less, while micropolarity higher,in UNDE solution than those in UNDA’s. Therefore, conformation of the hydrophobic chain in aggregates is infered to be more bending for UNDE. Changes of thermodynamic parameters in micellization and adsorption show smaller free energy reduction and larger increases in entropy and enthalpy for UNDE than those for UNDA.
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