Synthesis, Micellization, and Surface Activity of Novel Linear‐Dendritic Carboxylate Surfactants

Abstract

Two generations of novel linear-dendritic carboxylate surfactants C 18-G 1-(COONa) 2 and C 18-G 2-(COONa) 4 have been synthesized by the divergent method and their structures are characterized by 1 H Nuclear Magnetic Resonance and Infrared analysis. The electrical conductivity measurement is used to measure the Krafft temperatures of C 18-G 1-(COONa) 2 and C 18-G 2-(COONa) 4 , which are much smaller than those of the corresponding conventional surfactant sodium stearate. The markedly enhanced solubility of two linear-dendritic surfactants is ascribed to the high hydrophilicity of surfactant headgroups induced by the carboxylate and ester groups. The critical micelle concentration (CMC) values obtained from both the electrical conductivity and surface tension measurements indicate that the micellizations of linear-dendritic surfactants become favorable with the increase in the number of the surfactant headgroup. However, the surface activity parameters including the surface tension at the CMC, maximum surface excess, and minimum surface area reveal that C 18-G 1-(COONa) 2 exhibits greater efficiency in absorbing at the air/water interface compared to C 18-G 2-(COONa) 4 , owing to their different steric repulsions of the surfactant headgroups. In addition, C 18-G 1-(COONa) 2 and C 18-G 2-(COONa) 4 have higher emulsifying ability than the conventional surfactants sodium stearate and sodium octadecyl sulfate.

Multiheaded Cationic Surfactants with Dedicated Functionalities: Design, Synthetic Strategies, Self-Assembly and Performance

“…The starting ("initial") building blocks for a surfactant with a single hydrophobic chain comprise, generally, simple and commercially available organic compounds, such as fatty alcohols or amine, carboxylic acid, or alkyl halide with a long hydrocarbon motif [22,33,34]. Conversely, the synthesis of the starting blocks for gemini-type or oligomeric-type surfactants may involve multistep reactions, providing the formation of a multifunctional compound containing multiplied hydrophobic groupings [35].…”

“…Conversely, the synthesis of the starting blocks for gemini-type or oligomeric-type surfactants may involve multistep reactions, providing the formation of a multifunctional compound containing multiplied hydrophobic groupings [35]. In general, the synthesis of the abovementioned derivatives comprises multiplied reactions such as alkylation of diamines (e.g., the reaction of an alkyl halide with ethylenediamine), Michael addition or amine-cyanuric anhydride coupling [22,36]. Such an approach desires appropriate purifications of the obtained intermediates to obtain the required purity of the final product.…”

“…Dendronic head groups possess very different structural features than simple surfactant head groups, and their self-assembly behavior differs from that of conventional surfactants. They reveal special aggregation behavior in the solution and at the interfaces, along with some important advantages such as a controllable molecular structure, geometric symmetry of molecular configuration, variable types and a number of functional groups [22]. In the literature, there are some reports on the dendrimeric polymer amphiphiles (often so-called dendritic polymeric surfactants), their synthesis, aggregation and application properties [23].…”

“…In the literature, there are some reports on the dendrimeric polymer amphiphiles (often so-called dendritic polymeric surfactants), their synthesis, aggregation and application properties [23]. However, they constitute derivatives with relatively high polydispersity, whereas dendrimeric surfactants (see Scheme 1), products of low molecular weight, have fixed molecular mass, high solubility and easily controllable aggregation behavior [21,22]. The branched and multiheaded surfactants (Scheme 1: bicephalic, gemini, trimeric representatives) can be considered initial generations of linear dendritic surfactants.…”

“…Wang et al synthesized a group of surfactants with multiple headgroups by grafting a dendritic unit of poly(amidoamine) onto an octadecyl chain, which formed vesicles in aqueous solutions at pH > 5 [24]. Recently, two generations of carboxylate surfactants C18-G1-(COONa) 2 and C18-G2-(COONa) 4 have been synthesized and characterized by Lou et al [22]. However, the literature rarely describes linear dendritic structures with a strictly symmetric configuration.…”