## 2 Results and Discussion  
The morphology-controlled AIE fluorescent microspheres were synthesized by two-step dispersion polymerization by using styrene (St) as a nucleating monomer, polymerizable cationic monomer 2-(methacryloyloxy)-N, \(N\), \(N\)-trimethylethanaminium chloride (DMC) as the copolymer and stabilizer, 2-(4-Vinylphenyl)ethene-1,1,2-triyl)tribenzene (TPEE) as the AIE fluorescent functional monomer, and divinylbenzene (DVB) as the crosslinking agent, which was shown in Scheme 1a. The morphology of the synthesized fluorescent microspheres was controlled by changing the amount of reaction parameters, such as DMC, DVB, and TPEE. Figure 1 shows SEM images of poly(styrene-co-(2-(4-Vinylphenyl)ethene-1,1,2-triyl)tribenzene) (PS@TPEE) fluorescent microspheres prepared by two-step dispersion polymerization using DMC stabilizer concentrations ranging from 0.025 to 3 wt% (Table S1, entries 1-9). When the concentration of DMC was 0.025 wt%, the resulting fluorescentPS@TPEE microspheres showed obvious polydispersity, as shown in Figure 1a. This was due to the amount of stabilizer being too small, and not enough to stabilize the nucleus after nucleation, resulting in nuclear aggregation and the formation of large particles. As the amount of DMC stabilizer increased from 0.05 wt% to 2 wt%, monodispersive apple-shaped PS@TPEE fluorescent microspheres were successfully synthesized, as shown in Figure 1b-h. When DMC concentration increased to 3 wt%, PS@TPEE fluorescent microspheres obtained were polydispersed as spherical with coagulation and secondary particles, as reported by [PERSON] et al. [58]. The content of the crosslinker is another one of the most important parameters affecting the particle size distribution and morphology in the dispersion polymerization process. Therefore, in order to explore the effects of different amounts of DVB on the monodispersity and morphology of microspheres, a series of experiments were carried out to change the content of DVB under other constant conditions. As shown in Figure 2, the pristine PS@TPEE fluorescent microspheres prepared without DVB were monodisperse and spherical. Non-spherical PS@TPEE fluorescent microspheres with apple-like morphology were obtained with the addition of DVB (Figure 2b-d). When the amount of DVB exceeded 2% relative to monomer, the PS@TPEE fluorescent became spherical again. This may be because, with the addition of crosslinking agent DVB, a crosslinked layer was formed on the surface of PS@TPEE fluorescent microspheres, and there was still a large amount of unreacted styrene monomer inside, which was a good solvent for polystyrene. Therefore, when the crosslinking agent was relatively small (0.5-2 wt% relative to styrene monomer), the crosslinked layer formed on the surface was not enough to support the internal structural collapse caused by the dissolution of polystyrene polymer to form an apple-like morphology (Figure 2b-d) [58; 59]. With the further increase of DVB amount, the crosslinking density of the formed crosslinking structure increased, and the crosslinking strength was enhanced enough to maintain spherical stability, so the morphology of PS@TPEE fluorescent microspheres changed from heterogeneous structure to spherical structure again (Figure 2e-h). When the amount of DVB  
Figure 1: SEM images of PS@TPEE fluorescent microspheres prepared with different amounts of DMC (relative to St): (**a**) 0.025 wt%, (**b**) 0.05 wt%, (**c**) 0.1 wt%, (**d**) 0.3 wt%, (**e**) 0.5 wt%, (**f**) 1 wt%, (**g**) 1.5 wt%, (**h**) 2 wt%, (**i**) 3 wt%. Other reaction parameters: St (2.00 g), AlBN (0.04 g), TPEE (0.02 g), DVB (0.02 g), reaction medium ethanol–water (14.4 g/3.6 g, 80:20, \(w\)/\(w\)). increased to 12 wt%, the crosslinked network on the surface of the microspheres became extremely compact, making it difficult for St to enter the interior of the particles, resulting in the secondary nucleation of the microspheres, and the latter sticking to each other and becoming polydisperse, as shown in Figure 2i.