This is a review article on the rheological properties of mixed solutions of sulfonated methyl esters (SME) and cocamidopropyl betaine (CAPB), which are related to the synergistic growth of giant micelles. Effects of additives, such as fatty alcohols, cocamide monoethanolamine (CMEA) and salt, which are expected to boost the growth of wormlike micelles, are studied. We report and systematize the most significant observed effects with an emphasis on the interpretation at molecular level and understanding the rheological behavior of these systems. The experiments show that the mixing of SME and CAPB produces a significant rise of viscosity, which is greater than in the mixed solutions of sodium dodecyl sulfate and CAPB. The addition of fatty alcohols, CMEA and cationic polymer, leads to broadening of the synergistic peak in viscosity without any pronounced effect on its height. The addition of NaCl leads to a typical salt curve with high maximum, but in the presence of dodecanol this maximum is much lower. At lower salt concentrations, the fatty alcohol acts as a thickener, whereas at higher salt concentrations -as a thinning agent. Depending on the shape of the frequency dependences of the measured storage and loss moduli, G' and G", the investigated micellar solutions behave as systems of standard or nonstandard rheological behavior. The systems with standard behavior obey the Maxwell viscoelastic model (at least) up to the crossover point (G' = G") and can be analyzed in terms of the Cates reptationreaction model. The systems with nonstandard rheological behavior obey the Maxwell model only in a restricted domain below the crossover frequency; they can be analyzed in the framework of an augmented version of the Maxwell model. The methodology for data analysis and interpretation could be applied to any other viscoelastic micellar system.

Here, we present results from a systematic study on cleaning of oily deposits from solid surfaces (porcelain and stainless steel) by solutions of fatty acid sulfonated methyl esters (SME), sodium salts. The zwitterionic dodecyldimethylamine oxide (DDAO) has been used as a cosurfactant. As representatives of the vegetable and mineral oils, sunflower seed oil and light mineral oil have been used. The process of oil drop detachment from the solid substrates (roll-up mechanism) has been monitored. In the case of porcelain, excellent cleaning of oil is achieved by mixed solutions of SME and DDAO. In the case of stainless steel, excellent cleaning (superior than that by linear alkylbenzene sulfonate and sodium lauryl ether sulfate) is provided by binary and ternary mixtures of SME, which may contain also DDAO. For the studied systems, the good cleaning correlates neither with the oil/water interfacial tension, nor with the surfactant chainlength and headgroup type. The data imply that governing factors might be the thickness and morphology of admicelle layers formed on the solid/water interface. The results indicate that the SME mixtures represent a promising system for formulations in house-hold detergency, having in mind also other useful properties of SME, such as biodegradability, skin compatibility, and hard water tolerance.

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"Methyl ester sulphonates (MES), which are produced from renewable vegetable oil-based materials and have an ISO 16128 natural origin index of 0.84, are promising new surfactants for conditioning hair shampoos. Previous studies have shown that MES has low skin irritation potential (i.e., mild to the skin), provides easier deposition of conditioning agents compared to sodium lauryl ether sulphate (SLES), and readily delivers desired rheology profiles. A drawback of MES is that it has poor solubility at low temperatures. The Krafft temperatures (TK) of MES-C16 and MES-C18 are 28 °C and 41 °C, respectively, which can be lowered substantially by using eutectic mixtures of MES-C16 and MES-C18; for example, MES-C16/C18 (3:1, w/w) has a TK of 15 °C. At temperatures below 15 °C, all mixtures of MES-C16 and MES-C18 are turbid due to the formation of MES crystals, and phase separation could occur during long-term storage. The solubility of MES could be further improved by incorporating the MES molecules into the micelles of other surfactants. In this study, the solubility of MES in pure water at 5 °C in the presence of alkyl polyglucosides (APG) was investigated. The results showed that the solubility of MES improved by > 28 times in the presence of APG at low total surfactant concentrations and predicts that at higher total surfactant concentrations, solutions of MES and APG will remain transparent at 5 °C when the weight fraction of MES-C16, MES-C18, MES-C16/C18 (80:20), and MES-C16/C18 (60:40) are below 28 %, 15 %, 35 %, and 38 %, respectively. Predictions for MES-C16/C18 (80:20) and MES-C16/C18 (60:40) were verified using 25 % total surfactant concentration and storage at 5 °C for 12 weeks. MES/APG-based surfactant systems have promising potential in hair shampoo applications, because both surfactants have low skin irritation potentials and are produced from renewable raw materials."