Sweet Surfactants: Packing Parameter-Invariant Amphiphiles as Emulsifiers and Capping Agents for Morphology Control of Inorganic Particles

Carbohydrate-based surfactants are a green class of biodegradable, low toxic, nonionic surfactants. The widely used subclass of alkyl-glycosides is of special interest, since established models used to describe common surfactants (HLB-value, packing parameter) lack the capability to predict the differing behaviour of different carbohydrate-isomers or anomers. Therefore, these sugar-based surfactants are ideal models for investigating how small structural changes in their structure affect their amphiphilic properties [1]. 

Here, we present the preparation of a comprehensive library of well-defined alkyl-glycoside surfactants varying in choice of head-group, anomeric configuration and length of the alkyl chain, including a novel class of glycosurfactants bearing an internally unsaturated alkyl chain [2]. We systematically studied the effect of these parameters on the surfactant properties by applying a multitude of analytical methods, such as isothermal titration calorimetry (ITC), tensiometry, dynamic light scattering (DLS), small angle-X-ray scattering (SAXS) and transmission electron microscopy (TEM). In addition, we evaluated the emulsification properties of the glycosurfactants. Finally, we investigated the role of these surfactants as capping agents in the generation of zinc oxide (ZnO) nanoparticles and we show their marked effect on the shape of the formed, inorganic nanocrystals.