Study of the pH-Induced Self-assembly of Conjugated Linoleic Acid/Conjugated Linoleate in an Aqueous Solution

摘要

Conjugated linoleic acid (CLA) was prepared by alkali isomerization from linoleic acid (LA) with KOH as catalyst and ethylene glycol as solvent. When w(KOH):w(LA):v(ethylene glycol)=l:2:3 at 170 °C for 4 h, the purity of CLA was as high as 95 %. The chemical structure of the surfactant was confirmed by FTIR, GC, GC-MS. Depending on the pH, conjugated linoleic acid/conjugated linoleate self-assembled into different types of aggregates. The critical micelle concentration (omc), surface tension at the cmc (λ_(cmc)), the maximum surface excess concentration at the air/water interface (Γ_(max)) and the minimum area per surfacatant molecule at the air/water interface (A_(min)) of sodium conjugated linoleate were 0.424 mmol·L~(-1), 30.77 mN·m~(-1), 3.29×10~6 mol·m~(-2) and 0.505 nm~2 at pH 13 in 0.1 mol'L"1 NaOH aqueous solution with excess NaCl. Subsequent, the morphology of sodium conjugated linoleate self-assembly aggregates were cross-linked to fix the microstructers of the self-assembly aggregates.