Ethanol-induced coacervation in aqueous gelatin solution for constructing nanospheres and networks: Morphology, dynamics and thermal sensitivity

Ethanol was used to induce coacervation in aqueous solutions of gelatin. Coacervation resulted from phase separation driven by ethanol as a poor solvent forgelatin, impacting aggregation of gelatin chains. Static coac-ervation was performed to investigate coacervate morphology, and gelatin concentration and ethanol temperature influenced the morphologies of the gelatin coacervates. High-concentration gelatin solutions (4.8 wt%) treated with lower temperature ethanol (<25 degrees C) formed network morphologies, while low concentration gelatin solution (<4.8 wt%) treated with ethanol near room temperature formed nanosphere assemblies. Dispersive nanospheres were obtained after treatment with higher temperature ethanol (similar to 45 degrees C). Stirring the mixture of gelatin solution and ethanol resulted in dispersed nanospheres where the size was adjusted by changing the volume ratio of aqueous gelatin solution and ethanol (VGel:VEtOH) and the gelatin concentration. Turbidity and absorbance measurements were carried out to further investigate coacervation dynamics. The cocervation system reached dynamic equilibrium according to the VGel:VEtOH, suggesting phase separation and molecular arrangements were key. DLS results showed that reversible changes in coac-ervate radius could be attained by periodic heating and cooling cycles (25-60 degrees C). This work provides useful information for constructing gelatin-based materials using a facile coacervation method. (c) 2020 Elsevier Inc. All rights reserved.

Automated summary

Ethanol was used to induce coacervation in gelatin aqueous solutions, resulting in different morphologies of gelatin coacervates depending on gelatin concentration and ethanol temperature. High-concentration gelatin solutions formed network morphologies when treated with lower temperature ethanol, while low concentration solutions formed nanosphere assemblies with ethanol near room temperature. The size and morphology of coacervates could be adjusted by changing the volume ratio and temperature.