Synthesis And Properties Of Alkyl-tetra(Ethoxy)-β-d-glucopyranoside And Alkyl Glucoside Surfactants

Alkyl glycosides（APG）are green,mild,and highly effective carbohydrate derived nonionic surfactants,which are produced from natural renewable resources and have many advantages such as low toxicity,excellent properties,and ecological safety.The surfactants with medium and long alkyl chain lengths of APGs show higher activities in applications than many surfactants,therefore,it is attractive in catalytic and adsorption applications,nanotechnology,analytical separations,food processing,biotechnology,ecological lubricants,environmental remediation and oil recovery enhancement.APG is a potential and sustainable substitute for the synthesis of surfactants from fossil materials.Studies have shown that better water solubility makes it have greater potential application value.In order to solve the inherent problem of poor water solubility of traditional alkylβ-D-glucopyranoside,a series of glycosides（n=7-18）with different hydrophobic chain lengths were successfully synthesized by introducing oligooxyethylene fragments to carry out structural modification.Their solubility,hydrophilic-lipophilic balance value,log P value,foamability and foam stabilization,emulsification,hygroscopicity,surface activity,thermotropic liquid crystal and lyotropic liquid crystal phase behavior have been studied.The relationship between the structure of this series of glycosides and the physical and chemical properties was revealed.The results showed that with the increase of the alkyl chain,the solubility and HLB value gradually decreased,while the log P value gradually increased,Octadecyl tetra（ethoxy）β-D-glucopyranoside was insoluble in water at 25°C.Taken together,long-chain alkyl glycosides had good foaming properties and excellent emulsifying properties.Among them,dodecyl tetra（ethoxy）β-D-glucopyranoside had the best foaming performance.In the toluene/water and n-octane/water systems,tetradecyl tetra（ethoxy）β-D-glucopyranoside had the best emulsification ability.In the rapeseed oil/water system,cetyl tetra（ethoxy）β-D-glucopyranoside had the best emulsifying ability.This series of glycosides reduced the surface tension of aqueous solutions to nearly 28 N·m^-1 at their critical micelle concentration,and they had good surface activity.The synthesized glycosides were remarkably thermotropic liquid crystalline,and alkyl tetra（ethoxy）β-D-glucopyranosides（n=8-18）with alkyl chain lengths n=8-18 showed excellent lyotropic liquid crystalline phase behavior.Alkyl glucosinolates,as a kind of sulfur-containing sugar-based nonionic surfactants,mainly exist in cruciferous plants.Because of its excellent biological functions,it has received widespread attention.However,compared with other types of alkyl glycosides,thioalkyl glycosides are less studied.In this chapter,glucose and mercaptan were used as raw materials.Under the catalysis of boron trifluoride ether,the acylated glucose and mercaptan were coupled and deprotected to form a series of alkylα-D-glucopyranosides with different alkyl chain lengths,and its structure was characterized by ¹H NMR,¹H ¹H COSY,mass spectrometry,optical rotation,etc.And its HLB value,log P value,solubility and liquid crystallinity were studied.Its liquid crystal properties have been studied.