## 3 Experimental Section
The products were dried under vacuum for 24 h at R.T. [C6 VIm]Br was obtained as white solid. Yield: 71%. [C6 VIm]Br: \({}^{1}\)H-NMR (D2O, 400 MHz, ppm): 7.57 (1H, s); 7.37 (1H, m); 6.93 (1H, m); 5.60 (1H, d); 5.22 (1H, d); 4.04 (2H, t); 1.70 (2H, s); 1.17 (2H, s). \({}^{1}\)H-NMR (DMSO, 400 MHz, ppm): 9.66 (1H, s); 8.24 (1H, t); 7.99 (1H, t); 7.33 (1H, m); 5.99 (1H, m); 5.43 (1H, m); 4.22 (2H, t); 1.83 (2H, d); 1.31 (2H, s). \({}^{13}\)C-NMR (DMSO, 100 MHz, ppm): 135.36, 128.88, 123.31, 119.23, 109.04, 49.02, 28.80, 24.77. ESI-MS (_m/z_): calcd. for C16H24N4 Br2: 432.2, found: 432.2. Elemental analysis (%): Calculated: C, 44.46; H, 5.60; N, 12.96; Br, 36.98. Found: C, 42.94; H, 5.36; N, 12.50; Br, 39.20. M.P. : 219 \({}^{\circ}\)C.  
_1,8-Octanediyl-3,3'-bis-1-vinyl imidazolium bromide ([CsVIm]Br)_ 1-vinyl imidazole (0.94 g, 10 mmol) and 1,8-dibromooctane (1.36 g, 5 mmol) were dissolved in methanol (50 mL) in a round-bottom flask fitted with a condenser and N2 bubbler. Subsequently, the mixture was stirred at 80 \({}^{\circ}\)C for 48 h under a nitrogen atmosphere. After then, the reaction mixture was precipitated from diethyl ether (150 mL), and recrystallized twice from diethyl ether. The products were dried under vacuum for 24 h at R.T. Yield: 27%. [CsVIm]Br: \({}^{1}\)H-NMR (D2O, 400 MHz, ppm): 8.868 (1H, s); 7.598 (1H, d); 7.398 (1H, d); 6.969 (1H, m); 5.605 (1H, m); 5.255 (1H, m); 4.057 (2H, t); 1.724 (2H, m); 1.152 (4H, s). \({}^{13}\)C-NMR (D2O, 100 MHz, ppm): 128.39; 122.97; 119.61; 109.47; 50.07; 29.15; 28.00; 25.37. ESI-MS (_m/z_): calcd. for C18H28N4 Br2: 460.26, Found: 460.1. Elemental analysis (%): Calculated: C, 47.15; H, 6.16; N, 12.23; Br, 34.46. Found: C, 47.40; H, 5.73; N, 11.87; Br, 35. Mp: 173-175 \({}^{\circ}\)C.  
_1,12-Dodecanediyl-3,3'-bis-1-vinyl imidazolium bromine ([C12]YIm]Br)_ 1-vinyl imidazole (0.94 g, 10 mmol) and 1,12-dibromododecane (1.64 g, 5 mmol) were dissolved in methanol (50 mL) in a round-bottom flask fitted with a condenser and N2 bubbler. Subsequently, the mixture was stirred at 80 \({}^{\circ}\)C for 48 h under a nitrogen atmosphere. After then, the reaction mixture was precipitated from diethyl ether (150 mL), and recrystallized twice from diethyl ether. The products were dried under vacuum for 24 h at R.T. Yield: 60%. [C12]Br: \({}^{1}\)H-NMR (D2O, 400 MHz, ppm): 8.80 (1H, s); 7.53 (1H, s); 7.33 (1H, s); 6.88 (1H, m); 5.55 (1H, m); 5.17 (1H, d); 3.98 (2H, t); 1.64 (2H, s); 1.03 (8H, d). \({}^{13}\)C-NMR (D2O, 100 MHz, ppm): 134.21, 128.34, 122.94, 119.51, 109.34, 50.06, 28.68, 25.39. ESI-MS (_m/z_): calcd. for C22H36N4 Br2: 516.36, Found: 516.2. Elemental analysis (%): Calculated: C, 51.17; H, 7.03; N, 10.85; Br, 30.95. Found: C, 50.34; H, 6.86; N, 10.62; Br, 32.18. Mp: 134.2 \({}^{\circ}\)C.  
_Cross-linking copolymerization of [C\({}_{n}\)VIm]Br and EgDMA_ Biimidazolium (BIm)-based nanogels were prepared by conventional radical copolymerization of [C\({}_{n}\)VIm]Br and cross-linkers using AIBN as initiator in selective solvents. The following example describes the typical synthesis of nanogel using 500 mol % [C\({}_{n}\)VIm]Br based on EgDMA. This protocol is representative of all nanogel syntheses. [C\({}_{6}\)VIm]Br (2.12 g, 4.9 mmol), EgDMA (0.194 g, 0.98 mmol), and AIBN (0.021 g, 0.13 mmol) were dissolved in methanol (50 mL), and the mixture was stirred at 70 \({}^{\circ}\)C for 48 h. After then, the mixture was precipitated from diethyl ether (150 mL), and the products were washed with THF, and diethyl ether, respectively. The products were dried under vacuum for 24 h at 50 \({}^{\circ}\)C. (Yield: 62.5%). All the cycloaddition reactions were carried out in a 50 mL stainless steel reactor with magnetic stirrer and automatic temperature control system. After appropriate amounts of epoxides and catalyst were charged into, CO\({}_{2}\) was introduced in, and the pressure was kept constantly till the reaction was completed. Then the reactor was heated to desired temperature.