Micellisation and surface properties of oligo(oxyethylene) methyl-n-alkyl and di-n-alkyl ethers

Abstract

Two series of homogeneous diethers: A, CH₃(OCH₂CH₂)₈O(CH₂)_nH, n= 6, 8, 10, 12; B, H(CH₂)_n(OCH₂CH₂)₁₅O(CH₂)_nH, n= 5, 6, 7; have been prepared and studied in aqueous solution with respect to micellisation and adsorption at the air–water interface. The area per molecule in the adsorbed monolayer (± 10%) at the critical micelle concentration is 1.0 nm² for the samples of series A and 0.6 nm² for the samples of series B. For each series the free energy of micellisation (ΔG°) varies linearly with n, with a slope of ca.–2.8 kJ mol^–1 per CH₂ group and reaches its zero limit at n≈ 4.