The construction of pH responsive O/W1/W2 double emulsions based on carboxymethyl cellulose and chitosan: Structure, rheological behaviors and stability

In this study, the aim was to prepare pH responsive O/W 1 /W 2 double emulsions using carboxymethyl cellulose/chitosan (CMC/CS) via associative phase separation. The O/W 1 /W 2 double emulsions with different internal phase fractions (10 %, 20 %, 30 %, 40 %, 50 %, v /v) were prepared and the properties of the prepared O/W 1 /W 2 double emulsions was further investigated in the present work. The zeta-(ζ) potential and FTIR analysis confirmed that O/W 1 /W 2 double emulsions were mainly driven by electrostatic interaction and hydrogen bonding. The microstructure results showed that the O/W 1 /W 2 double emulsion droplet-aggregated gels with the highest double emulsion droplet density was formed as the internal phase fraction was 40 %, while the W 1 /W 2 interface of the O/W 1 /W 2 double emulsions was broken as the internal phase fraction was 50 %. Rheological property and stability results further confirmed that the O/W 1 /W 2 double emulsions with 40 % internal phase fraction had the best stability and dense network structure. In addition, CLSM result showed that the O/W 1 /W 2 double emulsions had excellent pH responsivity and the W 1 /W 2 interface had ion permeability and contractility. Furthermore, the rheology and stability results displayed that the prepared O/W 1 /W 2 double emulsions had pH reversibility. Therefore, this study provided a theoretical basis for the construction of pH responsive O/W 1 /W 2 double emulsion.