Aqueous Phase Behavior of Ultra-Long Polyoxyethylene Surfactants

Abstract

The aqueous phase behavior of poly(oxyethylene) alkyl ethers (C_mEO_n) having both ultra-long hydrophobic and hydrophilic chains (m =30 and n =94 and 42) was investigated. The HLB values of C₃₀EO₉₄ and C₃₀EO₄₂ are 18 and 16, respectively. In C₃₀EO₉₄ system, micellar solution phase (W_m), micellar cubic (I₁), hexagonal (H₁) and solid surfactant phases (S) are successively formed. The same sequence is observed for C₃₀EO₄₂ system, but the I₁ phase shrinks and the H₁ phase prevails over a wide range of composition. This phase sequence was compared to that of conventional poly(oxyethylene) surfactants and it was found that the surfactant layer curvature of aggregates becomes less positive in a long hydrocarbon-chain surfactant system even if the HLB values are the same.