## 2 Results and Discussion  
### Preparation of Core-Corona Polymer Microsphere Having Sulfonic Acid (CCM-SO\({}_{3}\)H)  
The preparation of CCM-SO\({}_{3}\)H is illustrated in Scheme 1. Benzyl chloride-functionalized polymer microsphere having phenylsulfonate **1** was prepared by the precipitation polymerization of styrene (St), divinylbenzene (DVB), and 4-vinylbenzyl chloride (VBC) [53]. The molar ratio of St/DVB/VBC was set to 60/20/20. The number-averaged diameter (D\({}_{n}\)) of the polymer microsphere was 1.14 \(\upmu\)m. Because the polydispersity (U) was quite low (1.00), monodispersed polymer microsphere **1d\({}_{20}\)C** was successfully obtained. **1d\({}_{20}\)C** means polymer microsphere synthesized from 20 mol % of divinylbenzene and 4-vinylbenzyl chloride (Scheme 1). The chlorine content measured by the halogen titration method (1.67 mmol g\({}^{-1}\)) was in good agreement with that calculated (1.68 mmol g\({}^{-1}\)). In addition to the monodispersed benzyl chloride-functionalized polymer microsphere with 20 mol % DVB, a monodispersed, poorly-crosslinked, benzyl bromide-functionalized polymer microsphere **1d\({}_{10}\)B** was successfully synthesized with a relatively higher yield (37%) by the precipitation polymerization of St, DVB, and a chemically cleavable divinyl crosslinker, followed by a transformation reaction [54]. From the FT-IR spectrum of **1d\({}_{10}\)B**, a new stretching vibration of the C-Br bond was observed at 1227 cm\({}^{-1}\) (Figure 1). These results indicate that both polymerization and transformation reaction successfully occurred. The D\({}_{n}\) of **1d\({}_{10}\)B** was 1.08 \(\upmu\)m with narrow size distribution (U = 1.13). The core-corona polymer microsphere functionalized with phenylsulfonate (CCM-SO\({}_{3}\)Ph) **2** was synthesized by the surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene (70 mol %) and phenyl \(p\)-styrenesulfonate (S) (30 mol %) by using **1d20C** or **1d10B** as a macroinitiator [55]. In the polymerization, benzyl chloride (BnCl) was simultaneously added as a sacrificial initiator. By the SEC analysis of the resultant free polymer initiated with BnCl, both M\({}_{\rm n}\) and M\({}_{\rm w}\)/M\({}_{\rm n}\) of the grafted polymersonto the surface of **1** were estimated. In FT-IR of **2**, two characteristic absorption peaks at 1376 and 1175 cm\({}^{-1}\) were observed for the stretching vibration of the S = O bond of phenylsulfonate (Figure 1). The M\({}_{\rm n}\) of the corona was successfully controlled by changing the M/I, and the M\({}_{\rm w}\)/M\({}_{\rm n}\) values were relatively low (\(<\)1.3). The M\({}_{\rm w}\)/M\({}_{\rm n}\) was increased with the increase of the M/I. We found that the SI-ATRP with low M/I proceeded in a controlled manner, and a well-defined CCM-SO\({}_{3}\)Ph was obtained. Compared with D\({}_{\rm n}\) (**1**), D\({}_{\rm n}\) (**2**) was increased when the grafted polymers were formed only by the initiators on the surface. D\({}_{\rm n}\) (**2**) became higher when increasing M/I from 50 to 200. The polydispersity (U) was low enough (\(<\)1.3). The CCM-SO\({}_{3}\)H **4** was prepared by the deprotection of phenylsulfonate moiety of **2**, followed by treatment with H\({}_{2}\)SO\({}_{4}\). For example, **4d\({}_{\bf 10}\)C** represents the CCM-SO\({}_{3}\)H synthesized from **1d\({}_{\bf 10}\)C** and SI-ATRP of styrene and \(p\)-styrenesulfonate with M/I = 50, and **4d\({}_{\bf 10}\)B-200** represents that from **1d\({}_{\bf 10}\)B** with M/I = 200. The deprotection reaction was conducted with NaOH aqueous solution in a 50/10/1 THF/CH\({}_{3}\)OH/H\({}_{2}\)O mixed solvent at 50 \({}^{\circ}\)C for 24 h. The characterization is summarized in Table 1. The yield was quantitative (93%-97%), and the sulfur content was in the range between 1.0 and 1.6 mmol g\({}^{-1}\). The absorption peaks at 1376 cm\({}^{-1}\) disappeared after the deprotection of phenylsulfonate moiety of **2** from the FT-IR spectra of **3** and **4** (Figure 1).