Abstract: The sodium carboxylate Gemini surfactants containing a p-phendioxy spacer, C_m+1-Ph-C_m+1(2cbx)·2Na(cbx means carboxylate, m+1=9,11,13), were synthesized and their micellization in aqueous solution was studied by using conductivity measurements.The critical micelle concentration (cmc) of C_m+1-Ph-Cm+1(2cbx)·2Na was found to be considerably low in aqueous solution.The regression equations of cmc-Twas shown as cmc=8.57×10^-4T2-0.499T+78.2 (m+1=9), cmc=2.86×10^-5T2-0.0146T+2.90(m+1=11) and cmc=1.43×10^-5T2-0.00730T+1.28(m+1=13), respectively.The variation of lncmc with (m+1) for all three surfactants obeyed an unified regression equation as lncmc=0.0323(m+1)²-1.00(m+1)+7.16. The thermodynamic functions calculated indicate that the micellization is an entropy-driven process and has a character of enthalpy-entropy compensation.In all the systems examined the micelle formed by (m+1)=11 is the most stable.

Key words: Sodium carboxylate Gemini surfactant, p-Phendioxy spacer, Synthesis, Micellization