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 FTIR 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 3.0wt% 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.