## 5 Conclusions  
A multiscale simulation study was conducted to investigate the stabilization mechanisms of water-in-oil HIPEs, with up to 70-80% water content, using DPD, MD, and DFT. A total of 42 emulsion models were simulated using three core emulsifiers (AS1-AS3) and fourteen oil types which revealed key relationships between molecular structure and emulsion stability. Among the tested emulsifiers, AS2 and AS3 exhibited significantly higher performance, achieving HIPE formation in 12 and 9 cases, respectively, compared to only 3 cases for AS1. The superior performance of AS2 and AS3 was attributed to enhanced interfacial dispersion, steric effects, and molecular polarity. Modified emulsifiers AS4 and AS5 further improved performance as they successfully stabilized HIPEs in all 14 oil cases for the benefit of optimized side-chain architecture and heteroatom inclusion.  
DFT results showed that AS4 and AS5 possessed dipole moments of approximately 6.1 Debye, whereas poorly performing emulsifiers AS1 and AS6 had values below 1.0 Debye. Emulsifiers with excessively high dipole moments, such as AS2 (10.04 Debye), exhibited moderate stability, indicating that an optimal polarity range enhances interfacial film formation. In contrast, the HOMO-LUMO energy gap (ranging from 0.029 to 0.082 Ha) and CED showed weak correlation with emulsification performance, suggesting that these descriptors are less reliable in predicting HIPE stability. Visualizations of orbital distributions confirmed that HOMO and LUMO regions were localized within the PAC as it limited electron delocalization and supported the dominance of non-bonding interactions in stabilization. Four distinct mechanisms of HIPE stabilization were identified: nanomicelle bridging, emulsifier-oil co-construction of interfacial films, side-group anchoring in interfacially inactive oils, and full interface coverage by emulsifier monolayers.  
Figure 11: HOMO and LUMO orbital distribution for emulsifier molecules showing localization within the PAC plane.  
This study demonstrates that dipole moment is the most predictive molecular property for HIPE stabilization, introducing a new descriptor for emulsifier design. These findings provide actionable criteria for the development of next-generation surfactants in petroleum recovery, chemical flooding, and complex emulsion technologies.  
Although these simulations provide valuable mechanistic insights into HIPE stabilization, the absence of direct experimental validation remains a notable limitation. To enhance the credibility and applicability of the findings, future research should incorporate experimental comparisons, particularly through interfacial tension measurements, microscopic characterization of emulsion microstructures, and rheological analyses. Additionally, the current DPD framework does not account for potential chemical adsorption or reactivity at the interface. Addressing this limitation will require the development and integration of reactive force fields capable of capturing chemical bonding phenomena relevant to complex emulsion systems.  
Methodology, M.H.O.O.; Software, X.F.; Validation, S.F.; Formal analysis, W.P.; Writing--review and editing, P.S.; Supervision, R.L.; Project administration, M.D. All authors have read and agreed to the published version of the manuscript.  
This research and the APC were funded by National Natural Science Foundation of China (Grant No. U19B2010, 42172347).  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors are deeply thankful for the financial support from the National Natural Science Foundation of China (Grant No. U19B2010, 42172347). The authors are also truly thankful for the help from the National Supercomputing Center in Shenzhen (Shenzhen Cloud Computing Center) of China in support of the computation.  
The authors declare no conflict of interest.