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Spontaneous Vesicle Phase Formation by Linear Pseudo-oligomeric Surfactant in Aqueous Solutions Nan Sun, Lijuan Shi, Fei Lu, Shuting Xie, Panpan Sun, and Li-Qiang Zheng Langmuir, Just Accepted Manuscript • DOI: 10.1021/la504913v • Publication Date (Web): 10 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015
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Spontaneous Vesicle Phase Formation by Linear Pseudo-oligomeric Surfactant in Aqueous Solutions Nan Sun,a Lijuan Shi,b Fei Lu,a Shuting Xie,a Panpan Suna and Liqiang Zheng*a a
Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China b
Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, China
------------------------------------------------------------------------------------------------------Corresponding author: Dr. LiqiangZheng E-mail address:
[email protected] Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China Phone number: +86-531-88366062 Fax number: +86-531-88564750
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Abstract In the present work, we reported a novel linear pseudo-oligomeric surfactant, which is formed by mixing dodecyl benzene sulfonate (SDBS) and a linear tricationic imidazolium bromide salt (LTIB) in a molar ratio of 3:1. The aggregation behavior, aggregate structures and interactions between SDBS and LTIB were investigated by surface tension measurement, dynamic light scattering, turbidity, cryogenic transmission electron microscopy and 1H NMR techniques. When SDBS is mixed with LTIB in aqueous solutions, three SDBS molecules may be “bridged” to one cationic LTIB molecule by intermolecular interactions, behaving like a linear oligomeric surfactant. Vesicles can be formed by this kind of linear pseudo-oligomeric surfactant. The aggregation behavior of the LTIB/SDBS mixed aqueous solutions behaves ratio- and concentration- dependence. Our work paves a convenient way for constructing surfactant systems with the characteristics of linear pseudo-oligomeric surfactant through intermolecular interactions between commercially available single-chain surfactants and linear tricationic imidazolium counter-ions.
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Introduction Oligomeric surfactants refer to surfactants containing three or more identical amphiphilic moieties chemically connected by spacer groups.
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Rich types of
aggregates, such as spherical micelles, threadlike micelles, wormlike micelles, ring like micelles and vesicles, can be conveniently constructed by self-assembly of oligomeric amphiphiles.6-16 Investigation on oligomeric surfactants has been expanded in many aspects due to their unique properties and aggregation behaviors. Yoshimura and Esumi synthesized a series of ring-type trimeric surfactants and found large aggregates can be formed in aqueous solution.6 Zana et al. reported linear trimeric and tetrameric quaternary ammonium surfactants and discovered that these surfactants formed branched threadlike micelles and closed ring-like coexisting with wormlike micelles.8,
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Wang’s group reported a series of star-shaped trimeric,
tetrameric, and hexameric cationic quaternary ammonium surfactants with amide-type spacer, which tend to form multiple kinds of aggregates in aqueous solution.9-11,17 However, the applications of oligomeric surfactants were limited due to the complicated synthesis and purification procedures. Exploiting simple ways to fabricate oligomeric surfactants would be of great necessity. For the sake of avoiding complicated synthesis procedures effectively, more attentions have been focused on applying noncovalent interactions, which is a possible convenient approach to construct desired organized molecular assemblies. Various noncovalent interactions have been used to create superamphiphiles, such as electrostatic attraction, hydrogen bonding, charge transfer interaction, metal-ligand
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coordination, host-guest recognition, π-π interactions. 18-21 Very recently, a kind of “pseudogemini” surfactants have attracted increasing attentions, which are constructed through noncovalent interactions between a connecting molecule and single-chain surfactant. Wang et al. and Feng et al. have reported novel kinds of “pseudogemini surfactants” which can form long thread-like micelles and pH-switchable wormlike micelles.22-24 Huang and co-workers found that oleic acid and diethylenetriamine can form DETA2+@2OA- building blocks in aqueous solution (8.0
