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Liu X.-G.,Key Laboratory of Biomedical Polymers Ministry of Education of China | Liu X.-G.,Hubei University | Xing X.-J.,Hubei University | Gao Z.-N.,Key Laboratory of Biomedical Polymers Ministry of Education of China | Gao Z.-N.,Hubei University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

Efficient synthesis of four star-like triethanolamine based cationic trimeric surfactants Tn (where n is the tail chain length, n=10, 12, 14, and 16) with ester groups in spacers has been successfully achieved, where mild reaction conditions were employed by substituting triethylamine (TEA) with potassium carbonate as the acid binding agent. The physicochemical properties of these surfactants were investigated by means of surface tension, electrical conductivity, and steady-state fluorescence measurements. The trimeric surfactants have been found to be capable of adsorbing to the air/water interface and orienting themselves through the interactions among the hydrocarbon chains. The conductivity measurement revealed the formation of premicellar aggregations in the T16 solution. It is noteworthy that the micropolarity of the surfactant aggregations decreased with the elongation of the hydrophobic chain length. Typically, dynamic light scattering and transmission electron microscopy studies showed that the aggregations of the four surfactants changed from larger ellipsoidal vesicles to smaller globule micelles with the increase of the surfactant concentration. It is assumed that this unusual aggregation behavior is related to the transformation of molecular conformation from stretched configuration to a pyramid-like shape. © 2014 Elsevier B.V.


Li B.,Key Laboratory of Biomedical Polymers Ministry of Education of China | Li B.,Hubei University | Zhang Q.,Key Laboratory of Biomedical Polymers Ministry of Education of China | Zhang Q.,Hubei University | And 4 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2015

A series of cationic gemini surfactants, butane-α,δ-bis-(dipropyl alkyl ammonium bromide), [CnH2n+1(CH3CH2CH2)2N(CH2)4N(CH3CH2CH2)2CnH2n+1]Br2 (where n is the tail chain length, n=10, 12, 14, and 16), referred to as CnC4Cn(Pr) were synthesized. The surface properties and aggregation behavior of these surfactants were investigated by measuring their surface tension, electrical conductivity, fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM). These gemini surfactants CnC4Cn(Pr) have a lower critical micelle concentration (CMC) than their corresponding monomer surfactants. Solution electric conductivity measurements indicated that premicellar aggregations were found in the C16C4C16(Pr) solution. Steady-state fluorescence measurements revealed that the C16C4C16(Pr) surfactant formed noncompact aggregate structures in solution over a wide concentration range. Interestingly, dynamic light scattering and transmission electron microscopy studies showed that the aggregations of the four surfactants were vesicle, which is not in accordance with the critical packing parameter (P) values obtained from Tanford's equation. To explain this unusual phenomenon, the volume of the component groups was used to calculate the hydrophobic volume and it was assumed that this phenomenon probably resulted from the face-to-face hydrophobic chains of these gemini surfactant molecules were inclined to be interdigitized in the aggregate. © 2015 Elsevier B.V.

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