## 2 Results and Discussion
### Interactions and Dispersion Stability of Anion-\(\pi\) Type PNPs with R-254 and Y-180
As shown in Figure 4f, the order of absolute \(\zeta\) values was consistent with the strength of the interactions between these PNPs and R-254. Furthermore, the salt-bridge H-bond formation resulted in higher stability for the mixtures of R-254 with PNPs-4 or PNPs-5. Next, the interactions between these PNPs and Y-180 were investigated. As shown in Figure 4g, a new peak was observed at 3672 cm\({}^{-1}\) in the mixtures of PNPs (except PNPs-1) with Y-180. This observation can be attributed to the fact that Y-180 has a greater number of H-bond donors compared to R-254. This characteristic enabled Y-180 to form salt-bridge H-bonds with a larger number of PNPs, resulting in an increased frequency of the [N-H-\(\cdots\)O]\({}^{-}\) peak [49]. In addition, the formation of classical H-bonds between PNPs-1 and R-254 resulted in a shift of the N-H peak to a higher frequency (Figure 4h, Table S7). Furthermore, the disruption and weakening of the intermolecular forces of Y-180 by the anions in the chains of these PNPs also shifted the C=O peaks to higher frequencies (Figure 4i). In the high-resolution XPS spectra of N 1s, a new peak was observed at 398.40 eV in the mixtures of PNPs (except PNPs-1) with Y-180, which was  
Figure 4: Interactions and dispersion stability of anion-\(\pi\) PNPs with R-254, using R-254 without PNPs as the control group. ATR-FTIR spectra in the ranges of **(a)** 3800–3300 cm\({}^{-1}\), **(b)** 3200–3100 cm\({}^{-1}\), and **(c)** 1700–1620 cm\({}^{-1}\). **(d)** High-resolution XPS spectra of N 1s. **(e)** Calculated proportions of N-H and [N-H-\(\cdots\)O]\({}^{-}\) peak areas in high-resolution XPS spectra of N 1s. **(f)**\(\zeta\) values in water. Interactions and dispersion stability of anion-\(\pi\) PNPs with Y-180, using Y-180 without PNPs as the control group. ATR-FTIR spectra in the ranges of **(g)** 3800–3400 cm\({}^{-1}\), **(h)** 3300–3100 cm\({}^{-1}\), and **(i)** 1760–1660 cm\({}^{-1}\). **(j)** Calculated proportions of N-H and [N-H-\(\cdots\)O]\({}^{-}\) peak areas in high-resolution XPS spectra of N 1s. **(k)**\(\zeta\) values in water. attributed to [N-H\(\cdots\)O]\({}^{-}\) (Figure S16). The proportion of [N-H\(\cdots\)O]- peak area gradually increased (Figure 4j). Moreover, all N-H peaks shifted to higher binding energies, while the proportion of peak areas gradually decreased, which indicated that the degree of dissociation of N-H\(\cdots\)O=C among Y-180 molecules gradually increased. All the peak parameters are listed in Table S8 of the Supporting Information. The above results jointly verified that the order of interactions' strength between these PNPs and Y-180 was as follows: Y-180 + PNPs-5 > Y-180 + PNPs-4 > Y-180 + PNPs-3 > Y-180 + PNPs-2 > Y-180 + PNPs-1. This order was consistent with the dispersion stability order for these mixtures. Furthermore, the mixture of R-254 with PNPs-5 exhibited the highest absolute \(\zeta\) value of 73.9 \(\pm\) 1.2 mV (Figure 4k). In conclusion, for both R-254 and Y-180, some of these PNPs significantly enhanced the dispersion stability of the pigments in water by forming classical and salt-bridge H-bonds. Interaction Mechanism of Anion-\(\pi\) Type PNPs with Pigments and Effect of Mixing Ratios of PNPs-5 with Four Pigments  
The characterization results mentioned above demonstrated that the mechanism of anion-\(\pi\) type PNPs acting as universal dispersants involved interactions with organic pigments through diverse non-covalent bond interactions. Furthermore, the interactions between PNPs and pigments were stronger than those between pigments themselves. This effectively weakened the pigment-pigment interactions, which was critical for enhancing the dispersion stability of organic pigments in water. Taking PNPs-5 as an example, the benzene rings in its chains formed \(\pi\)-\(\pi\) interactions with the benzene rings of CuPc, while the -PhSO3\({}^{-}\) established electrostatic interactions with Cu\({}^{2+}\).