## 2 Results and Discussion
### Characterization of Pigments with Different Types of Intermolecular Forces  
The intermolecular forces of organic pigments mainly include \(\pi\)-\(\pi\) stackings and H-bonds. The dispersion performance of organic pigments is closely related to the types of intermolecular forces, which are determined by their chemical structures. Based on their chemical structure, organic pigments can be classified into several categories: azo pigments (including monoazo and diazo), phthalocyanine pigments (including copper phthalocyanine and its halogenated derivatives), and cyclic ketone-based pigments (including diketopyrrolo-pyrrole, isoindoline, and anthracene ketones) [33]. Organic pigments belonging to these three structural classes exhibit high-performance characteristics, including excellent optical properties, durability, and favorable rheological properties. Following the Cyan Magenta Yellow Key (CMYK) color model, four organic pigments with distinct types of intermolecular forces were selected for investigation: Copper Phthalocyanine (CuPc), Carbon Black (CB), C.I. Pigment Red 254 (R-254), and C.I. Pigment Yellow 180  
Figure 1: Synthesis and physicochemical properties of anion-\(\pi\) type PNPs. (**a**) Schematic illustration of emulsion polymerization preparation. (**b**) SEM images. (**c**) Contact angles with water. (**d**) \(\zeta\) values in water. (**e**) \(\zeta\) values of PNPs-5 across the pH range of 0 to 14. (**f**) Dispersion photos of PNPs-5 in various solvents from high polarity to low polarity. (**g**) Viscosities at 5% content. (**h**) TGA curves from room temperature to 900 \({}^{\circ}\)C.  
(Y-180). These pigments were used to study their dispersion stability and the interaction mechanisms with five PNPs. Specifically, CuPc is a macrocyclic coordination compound characterized by a highly conjugated planar \(\pi\)-electronic structure [34]. This structure consists of Cu\({}^{2+}\) ions coordinated with planar Pc\({}^{2-}\) ligands (Figure 2a). The total number of atoms in the conjugated \(\pi\)-electron system is 40 (Table S2). CuPc exhibited rod-like morphology in transmission electron microscope (TEM) characterization with a primary particle diameter distribution of 108 \(\pm\) 16 nm (Figure S8). However, due to strong intermolecular \(\pi\)-\(\pi\) stackings, these primary particles tended to agglomerate when dispersed in water, resulting in an average particle size of 3.9 \(\upmu\)m. The \(\zeta\) value of CuPc was \(-8.8\)\(\pm\) 0.2 mV, indicating its poor stability in water. Additionally, the measured contact angle of water on the surface of CuPc in air was 140.6 \(\pm\) 0.6\({}^{\circ}\), suggesting that the surface of the pigment was strongly hydrophobic. For pigment CB, the carbon atoms in CB are arranged in a manner similar to graphite [35]. CB exhibited spherical morphology in TEM characterization with a primary particle diameter distribution of 36 \(\pm\) 7 nm (Figure S8, Table S2). CB aggregated with a particle size distribution of 1.4 \(\upmu\)m in water. The \(\zeta\) value of CB was \(-\)23.9 \(\pm\) 0.4 mV, and its hydrophobic surface exhibited a contact angle of 109.8 \(\pm\) 1.2\({}^{\circ}\) (Figure 2b). Moreover, the structure type of pigment R-254 is diketopyrrolo-pyrrole (DPP), and the number of hydrogen bond donors is two [36]. The type of intermolecular H-bond that are present is C=O\(\cdot\cdot\cdot\)N-H (Table S2) [33]. R-254 showed rod-like morphology in TEM  
Figure 2: Structural and physicochemical properties of four pigments. Structural formula, TEM image, particle size distribution curve, \(\zeta\) value, and contact angle of (**a**) CuPc, (**b**) CB, (**c**) R-254, and (**d**) Y-180. characterization with a primary particle diameter distribution of 190 \(\pm\) 35 nm (Figure S8). R-254 aggregated with a particle size distribution of 2.5 \(\upmu\)m in water. The \(\zeta\) value of R-254 was \(-\)10.5 \(\pm\) 0.04 mV, and its hydrophobic surface exhibited a contact angle of 132.3 \(\pm\) 1.9\({}^{\circ}\) (Figure 2c).