Alkyl di-/tri-/tetraoxyethyl β-D-xylopyranosides as derivatives of alkyl xylosides are a class of non-ionic sugarbased surfactants. They were stereoselectively synthesized by the Helferich method. Their properties including hydrophilic− lipophilic balance number, water solubility, surface property, foam property, emulsifying property, and thermotropic liquid crystal property were mainly investigated. The results showed that their water solubility decreased with increasing the alkyl chain length and increasing the number of the oligooxyethyl fragment. The critical micelle concentration had a monotonous decreasing trend with increasing the alkyl chain length. Nonyl di-/tri-/tetraoxyethyl β-D-xylopyranosides [−(OCH 2 CH 2 ) m −, where m = 2, 3, and 4] exhibited the most excellent foaming ability and foam stability. In the n-octane/water system, dodecyl tetraoxyethyl β-D-xylopyranosides and tetradecyl tetraoxyethyl β-D-xylopyranosides had the strongest emulsion ability. In addition, some alkyl di-/tri-/tetraoxyethyl β-D-xylopyranosides had thermotropic liquid crystal properties. Such sugar-based surfactants, alkyl di-/tri-/tetraoxyethyl β-D-xylopyranosides, will be expected to develop for a variety of practical application.

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Dioxyethene fragment (−(OCH2CH2)2−) was introduced into traditional alkyl β-d-glucopyranosides to ameliorate the water solubility, and eight nonionic surfactants, that is, alkoxy ethoxyethyl β-d-glucopyranosides with alkyl chain lengths (n = 6–16), were synthesized and characterized. Their hydrophilic and lipophilic balance number, water solubility, critical micelle concentration (cmc), γcmc, Γmax, and hygroscopic rate decreased with an increase in the alkyl chain length. Hexadecoxy ethoxyethyl β-d-glucopyranoside had no water solubility at 25 °C. Decoxy ethoxyethyl β-d-glucopyranoside had the best emulsifying property in the toluene/water and n-octane/water systems and the strongest foaming property, whereas dodecoxy ethoxyethyl β-d-glucopyranoside had the best emulsifying property in the rapeseed oil/water system. Such β-d-glucopyranosides (n = 6–12) exhibited excellent surface activity. In addition, for the binary mixture of alkoxy ethoxyethyl β-d-glucopyranosides (n = 8, 10, 12) and sodium dodecyl sulfate or cetyl trimethyl ammonium chloride, their cmc values were lower than the pure β-d-glucopyranosides, indicating that they had synergistic interactions. The fan focal conic textures of alkoxy ethoxyethyl β-d-glucopyranosides (n = 7–16) were observed during the cooling process under a polarizing optical microscope. Alkoxy ethoxyethyl β-d-glucopyranosides (n = 14, 16) had the related melting points and the clear points with differential scanning calorimetry. With β-d-glucopyranosides (n = 6–16) and n-butanol as the surfactant and cosurfactant, respectively, and with cyclohexane as the oil phase, the related microemulsion areas in their pseudoternary phase diagram system were investigated with the visual observation at 25 °C. Along with the slashing requirements of petroleum consumption, environmental protection, and green and sustainable development, nonionic sugar-based alkoxy ethoxyethyl β-d-glucopyranosides should be expected to have their potential practical application because of their strengthened hydrophilicity, improved water solubility, and enhanced surface activity.

Green surfactants alkyl glycosides are key to solve the inherent problem of water solubility due to their commercial application and extensive scientific research. Based on the enhancement strategy of hydrophilicity through the reconstruction of the conventional alkyl β-D-maltoside by introducing an oxyethyl group (−OCH 2 CH 2 −), D-maltose was used to prepare a series of nonionic disaccharide-based surfactants alkoxyethyl β-D-maltosides (4a−h, n = 6−16) so that the related water solubility was effectively improved, while the corresponding surface activity and other excellent properties were still maintained. Their physicochemical properties, including water solubility, surface activity, moisture absorption, and thermotropic liquid crystalline behavior, were investigated. The liquid crystal texture of alkoxyethyl β-D-maltosides (n = 7−16) has a fan-shaped focal conic texture. Furthermore, decoxyethyl β-D-maltoside had the strongest foaming characteristic and the best foam stability. Moreover, dodecoxyethyl β-D-maltoside (4f, n =12) had stronger emulsifying activity in the rapeseed oil/water system. Finally, CTAC/4f binary surfactants had an obvious synergistic effect. Such β-D-maltosides should have good application prospects in the future.

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