Aggregation Behavior in Water of Monomeric and Gemini Cationic Surfactants Derived from Arginine

Abstract

A new class of gemini surfactants, bis(Args) (Cn(LA)2, where n ) 3, 6, and 9), has been synthesized. Their solution and tension behaviors were studied and compared to those of the corresponding monomeric surfactant, LAM (N R -lauroylarginine methyl ester) and of a common cationic surfactant, CPC (cetylpyridinium chloride). Bis(Args) are made up of two symmetrical long chain N R -acyl-L-arginine residues of 12 carbon atoms linked by amide covalent bonds to an R,ω-alkylidenediamine spacer chain of varying length (n). By being produced from amino acid sources (arginine), these surfactants are biocompatible and less toxic to the environment. The solution behavior is also important for potential applications in foaming, agrichemical spreading aids, and cleaning processes, and in understanding the interfacial behavior. Strong evidence of two cmc's with different characters of aggregates was obtained from different techniques for the gemini surfactants but not for the monomeric surfactants. Surface tensiometry indicates that the geminis form aggregates of substantial size at 0.001-0.01 mM (at 25 °C) or at concentrations about 3 orders of magnitude lower than that of LAM. Fluorescence results and lower chloride counterion binding than that for LAM suggest that the aggregates are nonglobular. These methods reveal also a second cmc for larger globular aggregates at 0.09-0.5 mM. Conductivity measurements and calculations are consistent with the above inferences and were used to estimate the aggregation number N and the counterion binding parameter β. The nonglobular aggregates have lower β and smaller N values than the globular aggregates (micelles), and unlike conventional micelles, they tend to increase the molar conductivity compared to that of the pre-cmc solution.

Synthesis and Characterization of Highly Fluorinated Gemini Pyridinium Surfactants

“…Rosen et al [34] found that the occurrence of premicellar aggregates, especially for very short spacer gemini surfactants, caused the cmc, as determined by either surface tension or conductivity, to be substantially different in value. Similar results have been obtained by Pinazo et al [31] and Esumi et al [35] for hydrogenated gemini surfactants derived from arginine and for trimeric surfactants, respectively. They noticed that the cmc values obtained by fluorescence measurements and conductivity were similar to each other but larger than that determined by surface tension.…”

“…The observed increase in β and A min with increasing spacer length suggests the formation of non globular aggregates with lower aggregation numbers. [31] …”

Synthesis, Physicochemical Characterization, and Interaction with DNA of Long‐Alkyl‐Chain Gemini Pyridinium Surfactants

“…This phenomenon has been already reported in the literature. [48,57,58,74,75] Rosen et al tentatively introduced the CMCc/CMCsr atio to describe the extent of the difference of the CMC determined by different methods. [74] Analogously,wereported this parameter in Table 1.…”

“…Otherwise, anomalously higher values of specific conductivity than that expected (inset of Figure 1a nd Figures S1-S11o ft he Supporting Information) or maximai nm olar conductivity (L)p lots (Figure 5a nd Figures S12-S22 of the Supporting Information) are due to preaggregation phenomena. [57,62] Counterion bindingand surfaceminimum area…”

Straightforward Method for the Preparation of Lysine-Based Double-Chained Anionic Surfactants

“…Over the past decade, Infante and coworkers have been devoted to the synthesis of amino acidbased single-chain, double-chain, and gemini surfactants through employment of several chemical and chemoenzymatic methodologies and characterized their self-aggregation, biodegradability, and toxicity properties. [20][21][22][23][24][25][26][27][28][29][30] Among the different types of lipoamino acids created and studied by these authors, those derived from basic amino acids such as arginine presented interesting properties because of their low toxicity, high biodegradability, and antimicrobial activity. [26] The same research group has also explored some lysine-derived surfactants, including N a ,N e -dioctanoyl-lysine, which performed significantly better than classical anionic surfactants in terms of ocular and skin irritancy, haemolytic activity, antimicrobial properties, and aquatic toxicity.…”