Hydrophobic modification of dextran (degree of polymerization around 125) by reaction with 1,2-epoxydodecane was investigated in micellar aqueous medium in which epoxide was dispersed under magnetic stirring in the presence of a cationic surfactant. A base catalyst, sodium hydroxide, was added in water. Dextran derivatives with degrees of substitution up to 10% were prepared. Apart from dextran modification, epoxide molecules underwent interfacial oligomerization which led to by-products that had to be extracted by dialysis followed by Soxhlet extraction. Two main reaction parameters influenced the amount of oligomeric by-products, i.e. temperature and surfactant structure. Adsorption of these compounds at air/water interface was studied by surface tension and dilational rheology measurements and compared to that observed with amphiphilic dextrans prepared in homogeneous conditions.