## 4 Conclusions  
The core-corona polymer microsphere with sulfonic acid (CCM-SO\({}_{3}\)H) **4** was prepared by the surface-initiated ATRP (SI-ATRP) of styrene and phenyl \(p\)-styrenesulfonate with monodispersed benzyl halide-functionalized polymer microsphere **1** prepared via precipitation polymerization as a macroinitiator, followed by the regeneration of sulfonic acid. The ionic, core-corona polymer microsphere-immobilized chiral MacMillan catalyst (ICCC) **6** was successfully synthesized by the neutralization reaction between the CCM-SO\({}_{3}\)H **4** and MacMillan catalyst precursor **5**. The solvent effect and the structural effect of the catalyst was evaluated in the asymmetric Diels-Alder (DA) reaction of (\(E\))-cinnamaldehyde and 1,3-cyclopentadiene. We found that the increase of steric hindrance near the catalytic site by longer corona significantly decreased both the reactivity and enantioselectivity. The catalyst **6d1 oB** gave the DA adducts with 99% yields and excellent ee values (92% ee for the _exo_ isomer and \(>\)99% ee for the _endo_ isomer). The catalytic activity of the ionic, core-corona polymer microsphere catalyst was comparable to that of the linear-type polymeric catalyst. We conclude that the design of polymeric chiral organocatalyst, including the immobilization method and the support polymer, is of significance for improving the catalytic activity. The effect of the monomer and the diameter of **6** are under investigation.  
The following are available online at [[http://www.mdpi.com/2073-4344/9/11/960/s1](http://www.mdpi.com/2073-4344/9/11/960/s1)]([http://www.mdpi.com/2073-4344/9/11/960/s1](http://www.mdpi.com/2073-4344/9/11/960/s1)): Synthesis and characterization of **10** and **12d2 oC**. Figure S1: SEM image of **12d2 oC**, Figure S2: FT-IR spectra of **M-S, M-SNa, M-SH, and **12d2 oC**, Figure S3: \({}^{1}\)H NMR of **s53o** in CDCl3, Figure S4: \({}^{13}\)C NMR of **s53o** in CDCl3, Figure S5: \({}^{1}\)H NMR of **s53o** in CDCl3, Figure S6: \({}^{13}\)C NMR of **s53o** in CDCl3, Figure S7: \({}^{1}\)H NMR of **10** in DMSO-\(d_{\theta}\), Figure S8: \({}^{13}\)C NMR of **10** in DMSO-\(d_{\theta}\), Figure S9: FT-IR spectra of **53o, **s53 Na3o**, **s53H3o** and 10, Procedure for check of MacMillan catalyst leaching. Procedure for asymmetric Dieels-Alder reaction of (\(E\))-2-methoxycinnamaldehyde with 1,3-cyclopentadiene, Figure S10: \({}^{1}\)H NMR of crude **9** in CDCl3, Figure S11: \({}^{1}\)H NMR of **9** after purification in CDCl3, Figure S12: \({}^{13}\)C NMR of **9** after purification in CDCl3, Figure S13: \({}^{1}\)H NMR of crude **14** in CDCl3, Figure S14: \({}^{1}\)H NMR of **14** after purification in CDCl3, Figure S15: \({}^{13}\)C NMR of **14** after purification in CDCl3, Figure S16: \({}^{1}\)H NMR of **14** after reduction in CDCl3, Figure S17: \({}^{13}\)C NMR of **14** after reduction in CDCl3, Figure S18: GC chromatogram of racemic **9**. (a) Full chromatogram. (b) Expanded chromatogram, Figure S19: GC chromatogram of crude **9** (entry 7 in Table 4). (a) Full chromatogram. (b) Expanded chromatogram, Figure S20: GC chromatogram of **9** after purification (entry 7 in Table 4). (a) Full chromatogram. (b) Expanded chromatogram, Figure S21: HPLC chromatogram of crude **14** after reduction, Figure S22: HPLC chromatogram of **14** after reduction.  
Conceptualization, methodology, and supervision, N.H.; formal analysis and data curation, M.W.U.; writing--original draft preparation, M.W.U.; writing--review and editing, N.H. All authors read and approved the final manuscript.  
This research received no external funding.  
The authors are grateful to [PERSON] at Toyohashi University of Technology for useful discussions.  
The authors declare no conflict of interest.