Surface activity and micellization properties of chitosan-succinyl derivatives

Surface active chitosan-succinyl derivatives were prepared by incorporating hydrophilic succinyl group and different hydrophobic alkyl chains into chitosan through covalent bonding. Chemical structures of the derivatives were characterized by FTIR spectroscopy. Surface activity and critical micelle concentration values of the chitosan-succinyl derivatives were characterized by surface tension, conductivity and fluorescence measurements. Due to the surface inactivity and insoluble in common solvent or water, the application of chitosan is still a problem. The incorporation of succinyl group and alkyl chains significantly improves the surface activity of chitosan. Moreover, increasing the hydrophobic chain length leads to a smaller particle size and a higher stability of the emulsions of chitosan-succinyl derivatives.

For Chitosan-C12 as a typical example of chitosan-succinyl derivatives, the droplet charge density became less negative as pH value was increased from 3 to 5, but became more negative at higher pH value and remained nearly invariant at pH value above 8. All –COOH groups in Chitosan-C12 were neutralized by the incoming base to become –COO-groups and no additional negative ions were formed as pH value above 8, so that the zeta potential remained unchanged.Figure optionsDownload as PowerPoint slideHighlights
► The increase of amide I peak and decrease of amide II peak indicated the increase of amidation by grafting succinyl to chitosan.
► The surface excess concentration at cmc, Γcmc, is higher when the alkyl chain of a surfactant is longer.
► The more efficient the surfactant adsorption is. Chitosan-C12 is the most efficient surfactant evaluated by πcmc, pC20.
► The α value increases with the increase of alkyl chain. This result is probably due to the stronger hydrophobic forces.
► The alkyl side-chain of Chitosan-C12 is too long and hydrophobic to form more stable droplets.