pH-tolerant high internal phase Pickering emulsions stabilized by photo-responsive host–guest supramolecular polymers

High internal phase Pickering emulsions (HIPPEs) have attracted increased interest due to their diverse applications in fields such as food and material science. The pH value may vary in different application fields; however, maintaining the stability of HIPPEs at various pH levels presents a notable challenge. Here we describe photo-responsive HIPPEs tolerant to different pH values (pH = 2–12) with up to 96 % internal phase through one-step emulsification without pre-treatment (such as ultrasonic dispersion). The emulsifier was formed by the host–guest interaction between chitosan-grafted cyclodextrin (CS-CD) and azobenzene (C 4 AzoC 6 N). The microstructure of the porous materials prepared from the HIPPEs can be regulated by the photo-triggered adsorption of supramolecular polymers at the oil–water interface. Moreover, due to the photochromism properties of C 4 AzoC 6 N, a colour-changing writing ink can be obtained without any additive, making it an ideal candidate for 4D printing. This strategy provides a simple and efficient method for preparing pH-tolerant HIPPEs in a one-step process, expanding the range of applications in 4D printing and functional materials.