Physico-chemical studies and emulsifying properties of N-propyl-N-methylene phosphonic chitosan

► Low concentration solutions of chitosan derivative are formed by free molecules. ► At higher concentrations chitosan derivative form aggregates in several steps. ► In alkaline medium coiled molecules stretch and give a cooperative reaction. ► Derivative has emulsifying properties forming O/W emulsions. ► Emulsions have high stability to long time storage. Chitosan is a modified, natural carbohydrate polymer derived by deacetylation of chitin. Due to the presence of two functional groups can undergo many chemical modifications. In a previous work we described the synthetic strategy and characterization of a novel soluble derivative: N-propyl-N-methylene phosphonic chitosan (PNMPC). In the study of some physicochemical properties, results showed that this modified chitosan aggregates in several steps when the concentration is increased. By addition of NaOH the initially coiled molecules stretch exposing more phosphonic acid groups to neutralization and finally give a cooperative reaction with OH(. PNMPC has emulsifying properties and gives O/W emulsions with quasi-monodisperse small droplets. Emulsions with 0.18% PNMPC and 30:70 o:w ratio exhibited the best emulsifying properties within the test range. This emulsion ratio showed high stability to long time storage and several successive freeze/thaw and heating/cooling cycles.