Adsorption of gelatins on surfactant-free PS nanoparticles

The adsorption of gelatin chains on polystyrene (PS) latex nanoparticles was investigated by a combination of static and dynamic laser light scattering (LLS). The average mass of gelatin adsorbed on each nanoparticle (madsorbed) was calculated from the absolute scattered intensity, while the hydrodynamic volume (Vshell) of the adsorbed gelatin layer was obtained by dynamic LLS. In pure water, due to long-range electrostatic interaction, gelatin can act as stabilizer or flocculants, depending on the length, type and concentration of gelatin chains used. We found that in pure water, Vshell∝madsorbed; while in 2 wt% formamide aqueous solution, Vshell∝(madsorbed)2, indicating the shifting of the dominate interaction from electrostatic to hydrophobic. The adsorption was saturated at ∼2 mg/m2, nearly independent of pH and temperature. For a saturated adsorption, Vshell increases as the gelatin chain length increases. Our results indicate that the B-type gelatin with a lower molar mass and the pH range 7–9 are better choices for the stabilization of the nanoparticles in pure water.