Yue Wei1, Yanping Xie1, Zhixiang Cai1, Yalong Guo1, Min Wu1, Pengguang Wang1, Ruiqi Li1, Hongbin Zhang2. 1. Advanced Rheology Institute, Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, Shanghai 200240, China. 2. Advanced Rheology Institute, Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address: hbzhang@sjtu.edu.cn.
Abstract
HYPOTHESIS: The structural modification of natural emulsifiers may greatly impact their interfacial behaviours and bulk properties. The relationship between the microscopic interfacial viscoelasticity and the macroscopic emulsion stability in emulsifiers with different degrees of modification can be clarified using a multiscale approach. EXPERIMENTS: A polysaccharide emulsifier of corn fibre gum (CFG) with different octenyl succinate anhydride (OSA) contents was used to obtain a broad variety of interfacial properties. Interfacial adsorption kinetics and viscoelastic responses were measured by combining interfacial shear rheology and quartz crystal microbalance with dissipation monitoring, and the emulsion properties (droplet size and physical stability) at other scales were evaluated. FINDINGS: Compared with native CFG, esterified CFG formed thick interfacial films with higher elasticity and viscosity, and their corresponding emulsions showed greater stability. There exists a satisfactory correlation between interfacial rheological properties and emulsion stability. However, such a satisfactory correlation can not be established among the degree of esterification of CFG, interfacial viscoelasticity and stability since depletion flocculation might occur in the emulsion stabilized by the OSA-CFG with the highest OSA content, which induced inferior bulk stability but exerted no impact on the measured interfacial properties. We propose that the depletion flocculation is responsible for this imperfection and provide detailed explanations.
HYPOTHESIS: The structural modification of natural emulsifiers may greatly impact their interfacial behaviours and bulk properties. The relationship between the microscopic interfacial viscoelasticity and the macroscopic emulsion stability in emulsifiers with different degrees of modification can be clarified using a multiscale approach. EXPERIMENTS: A polysaccharide emulsifier of corn fibre gum (CFG) with different octenyl succinate anhydride (OSA) contents was used to obtain a broad variety of interfacial properties. Interfacial adsorption kinetics and viscoelastic responses were measured by combining interfacial shear rheology and quartz crystal microbalance with dissipation monitoring, and the emulsion properties (droplet size and physical stability) at other scales were evaluated. FINDINGS: Compared with native CFG, esterified CFG formed thick interfacial films with higher elasticity and viscosity, and their corresponding emulsions showed greater stability. There exists a satisfactory correlation between interfacial rheological properties and emulsion stability. However, such a satisfactory correlation can not be established among the degree of esterification of CFG, interfacial viscoelasticity and stability since depletion flocculation might occur in the emulsion stabilized by the OSA-CFG with the highest OSA content, which induced inferior bulk stability but exerted no impact on the measured interfacial properties. We propose that the depletion flocculation is responsible for this imperfection and provide detailed explanations.