Journal of Colloid and Interface Science, Vol.412, 95-99, 2013
The ability of single-chain surfactants to emulsify an aqueous-based liquid crystal oscillates with odd-even parity of alkyl-chain length
The physical properties of many organic molecules often oscillate when the number of carbons in their aliphatic chains changes from odd to even. This odd-even effect for single-chain surfactants in solution is rarely observed. Here, we report the ability of single-chain surfactants to emulsify a class of non-amphiphilic organic salts, disodium cromoglycate (5'DSCG) oscillates as a function of the odd or even number of the aliphatic carbons. This system provides a water-in-oil-in-water emulsion, in which aqueous droplets of 5'DSCG in liquid crystal phases are coated with single-chain surfactants in a bulk carrying aqueous solution. For both surfactants of CH3(CH2)(n)OSO3-Na+ and CH3(CH2)(n)COO-Na+, the ability to emulsify 5'DSCG molecules in water is stronger for surfactants with an odd number of sp(3)-hybridized carbon atoms in the aliphatic chains than those with an even number. This observed odd-even effect is consistent with the notion that conventional micelles possess a core of randomly arranged surfactant hydrocarbon tails. However, this water-in-oil-in-water resembles a vesicle system in which the surfactants assemble in a highly ordered structure that separates two aqueous systems. These new self-assembled phases have potential application in the formulation and design of new organic soft materials. (C) 2013 Elsevier Inc. All rights reserved.
Keywords:Odd-even effect;Disodium cromoglycate (5 ' DSCG);Chromonic liquid crystal;Single-chain surfactants;Water-in-oil-water emulsion