Emulsifying and stabilizing ability of alkylated chitosan

The emulsifying and stabilizing ability of alkylated chitosan was studied in comparison with initial chitosan during the preparation of simple emulsions and in the course of fabrication of polylactide microparticles through an oil/water emulsion solvent evaporation technique. The effect of chitosan chemical structure and solution characteristics (viscosity, surface tension, and hydrophilic lipophilic balance) on the emulsion properties (mean size and size distribution of the dispersed droplets, stability in time, emulsifying activity index, and emulsification stability index) and the polymer microparticles (total yield, mean size and size distribution, surface/volume morphology, and surface chemical composition) was evaluated. It was found that alkylated chitosan had better emulsifying and stabilizing abilities in comparison with unmodified chitosan at all studied concentrations (0.5-2 wt%) with a tendency to stabilization improvement when the concentration increased. The emulsions stabilized with the 2 wt% alkylated versus unmodified chitosan had a smaller average droplet size (48 ± 17 μm vs. 61 ± 23 μm), and the polymeric solutions at this concentration had a higher dynamic viscosity (53 mPa∙s vs. 43 mPa∙s), a lower HLB (22 ± 0.5 vs. 26 ± 0.5), and a surface tension (68 ± 0.5 mN/m vs. 72 mN/m). Alkylated chitosan has also proved to be a better emulsifier for stabilization of biodegradable microparticles giving a higher microparticle total yield (68.8 wt% vs. 46.6 wt%) of particles with a smaller mean size (291 ± 115 μm vs. 306 ± 164 μm).