From polymeric surfactants to colloidal systems (1): Amphiphilic dextrans for emulsion preparation

Polymeric surfactants have been prepared by chemical modification of a neutral bacterial polysaccharide, dextran. Various amounts of hydrocarbon groups (aliphatic chains or aromatic rings) were attached to the chains through the formation of ether links. The viscometric properties of their aqueous solutions are first described in the dilute and semi-dilute domain. A polynomial development of the usual Huggins equation is shown to conveniently depict the experimental results over the whole concentration range. The influence of the nature of hydrocarbon groups attached onto the polysaccharide backbone is discussed. The surface-active properties of amphiphilic dextran derivatives are examined at the oil–water interface, within the concentration range relevant for targeted applications. Submicronic oil-in-water emulsions are prepared by sonication in the presence of the polymeric surfactants. The influence of several operating parameters on the initial droplet diameter is examined. The more relevant parameter appears to be the duration of the sonication step. With the operation conditions used, the chemical structure of the polymeric surfactant does not have a significant influence on the initial droplet diameter while the weight ratio of polymer to oil is the relevant parameter.