## 3 Results and Discussion
### Stable Performance of MPNTS  
Hydrolytic stability is the focus of this study. The primary cause for the hydrolysis of trisiloxane is that the Si atom is relatively large and easily polarized. There are 3 d empty orbitals on the atom that can provide bonding conditions. In addition, the polarity Si-O bond is very strong, so it is easy to react with protonic acids, alkali metals, hydroxides, and water, resulting in a decrease in surface activity. Some related studies show that the hydrolysis of trisiloxane is another reason for this phenomenon. For example, [PERSON] et al. [32] believe that the hydrolysis of trisiloxane in acidic or alkaline conditions was due to the rearrangement of the Si-O-Si bond. Therefore, the pH [33] of the aqueous solution is also an important factor affecting its hydrolysis. However, there are relatively few related studies on the hydrolysis of trisiloxane. However, it is an essential consideration for some uses of silicone surfactants. We hope this study can provide a reliable direction for the research field of silicone surfactants. In order to determine the hydrolytic stability of MPNTS, the surface tensions changes of MPNTS in aqueous solutions at different pH values were measured for different periods of time (Figure 5a). The aqueous solutions of 0.1% (mass fraction) were prepared by adding the same dosage of MPNTS, and the pH values were adjusted to 3, 4, 5, 7, 9, and 10, respectively. The surface tensions of the samples were measured after standing for 3 h, 24 h, 7 d, 15 d, 45 d, and 60 d, respectively. We found that, after standing for 3 h, the surface tension of each aqueous solution at different pH was about 20 mN/m. After 24 h, the surface tension of aqueous solution at pH = 3 began to hydrolyze, and the surface tension rose sharply to 58.75 mN/m. However, it was still stable at other pH values. After standing until the 7 th day, the surface tension of the aqueous solution with pH = 3-5 increased, indicating that the aqueous solution had been hydrolyzed. Solutions at other pH values were still stable. After 15 days, the aqueous solutions in acidic conditions had been hydrolyzed nearly completely. After 45-60 days, the aqueous solution at pH = 7-10 was still stable and had not been hydrolyzed, and the surface tension was maintained at 18-20 mN/m. In order to further determine the hydrolytic stability of MPNTS, we prepared MPNTS aqueous solutions with pH = 7, 7.5, 8, 8.5, and 9, and we tested their surface tension changes for 60 days to determine the hydrolytic stability of MPNTS (Figure 5b). The results showed that the surface tensions of MPNTS did not change significantly after standing for 60 days in neutral and alkaline conditions, which proved that MPNTS did not undergo hydrolysis. MPNTS has good stability in neutral and alkaline environments, but it was easily hy  
Figure 5: The effect of time on the surface tension of MPNTS aqueous solutions in different pH values: (**a**) represents the change in surface tensions of pH = 3, 4, 5, 7, 9, and 10 with time; (**b**) represents the change in surface tensions of pH = 7, 7.5, 8, 8.5, and 9 with time. drolyzed in acidic conditions. This is due to the Si-O-Si bond in the MPNTS molecule being highly polar, and when it meets H\({}^{+}\) or OH\({}^{-}\) ions, it undergoes molecular rearrangement, resulting in the formation of two new molecules. However, these two molecules exhibit very poor surface properties in aqueous solutions. In acidic aqueous solution, H\({}^{+}\) has a strong attack on MPNTS, resulting in the hydrolysis of MPNTS within 24 h. In alkaline and neutral aqueous solutions, the introduction of EO(7) increases the hydrophilicity of MPNTS and its steric hindrance, making it more challenging for water molecules to attack MPNTS. Consequently, the hydrolysis reaction becomes difficult to proceed, and MPNTS can maintain high surface activity in neutral and alkaline environments. The aqueous solution of MPNTS shows good hydrolysis resistance at pH = 7-10, and the product can maintain a longer effective time.