Preparation and research of Diatomite@PNIPAm-stabilized Pickering emulsion with temperature responsiveness

Aiming at the shortcomings of the emulsion stabilized by surfactant due to toxicity and non-environmental protection, modified diatomite particles (DE), the temperature-responsive Pickering emulsion was studied. Due to the advantages of superior biocompatibility, DE have application potential in the field of cosmetics and pharmaceuticals. First, the Diatomite@MPS was obtained by silane coupling agent (MPS) hydrophobic modified DE. Then, modified DE (Diatomite@PNIPAm) with temperature responsiveness was synthesized successfully by grafting the temperature-responsive polymer poly N-isopropylacrylamide (PNIPAm). According to the characterization results of FT-IR testing and water contact angle testing, the diatomaceous earth was modified successfully. The TGA results showed that the optimal molar ratio of the Diatomite@PNIPAm prepared from MPS to NIPAm was 1∶1. Subsequently, oil-in-water (O/W) Pickering emulsions were prepared with Diatomite@PNIPAm as an emulsifier at different concentrations, and 3.0 wt% was determined as the optimal concentration. In addition, the emulsion was prepared with different oil-water volume ratios from 1∶9 to 9∶1 after determining the Diatomite@PNIPAm concentration, and the results showed that the oil-water volume ratio was 7∶3 as the best. The characterization results of Differential scanning calorimeter (DSC) testing showed that the lower critical solution temperature (LCST) of the Pickering emulsion was 40℃. The emulsion can undergo at least 6 demulsification-reemulsification cycles, and possesses excellent demulsification-reemulsification cycle performance.