Supporting information for Tuning the Catalytic Activity of L-Proline Functionalized Hydrophobic Nanogel Particles in Water

Materials. p-Toluenesulfonic acid monohydrate was purchased from Alfa Aesar. All other chemicals used were purchased from Sigma-Aldrich. Methyl methacrylate (MMA), ethyl methacrylate (EMA), n butyl methacrylate (n-BuMA), tert-butyl methacrylate ( t BuMA) and lauryl methacrylate (LMA) were filtered through a basic aluminium oxide column prior to use. 4-Nitrobenzaldehyde was filtered through a silica column prior to use. All other reagents were used without further purification.


Preparation of functional nanogel particles
Hydrophobic functional nanogels: For a typical synthesis (0.5 wt% CLD, 2 wt% DoF), sodium dodecyl sulphate (SDS) (0.20 g) was dissolved in 100 mL nanopure water before adding the cross-linker, ethylene glycol dimethacrylate (EGDMA) (0.025 mL).L-Proline functionalized methacrylate (0.020 g) and the hydrophobic comonomer methyl methacrylate (MMA) (1.0 mL) were then added under nitrogen flow with constant stirring.Finally, potassium persulfate (KPS) (0.005 g) was added and the reaction flask was immersed in a thermostatted oil bath set to 70 °C.After 12 hours continuous stirring at 800 rpm, polymerization termination was induced by cooling the reaction and allowing oxygen into the reaction vessel.Excess SDS was removed by dialysis against nanopure water.
Core-shell nanogels: 2 A 25 mL dispersion of the PMMA nanogels (50 wt% CLD) was heated to 70 o C and a degassed mixture of water (25 mL), SDS (0.063 g), t BuMA (0.125 g), EGDMA (0.125 g) and KPS (2.5 mg) were added under nitrogen using an automated syringe pump, at a rate of 25 mL/h.The polymerization was allowed to proceed for 12 hours at 70 °C before purification by dialysis against nanopure water to remove excess SDS.Scheme S1.Schematic representation of the synthesis of the L-proline functionalized PMMA nanogels and the core-shell nanogels.
Aldol reactions: typical procedure 4-nitrobenzaldehyde (0.038 g, 0.25 mmol, 1 eq) was dissolved in cyclohexanone (0.104 mL, 1 mmol, 4 eq) and mixed with the functionalized nanogel (0.0025 mmol, 1 mol%).The reaction mixture was sonicated for 5 minutes and then stirred at room temperature for 24 hours.THF/acetone (1:5) was added at the end of the reaction to induce swelling of the pores, making it possible to extract the reagents from the core of the particles Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2013 into the organic phase. 1 H NMR spectroscopy was then used to determine the percentage conversion and product diastereomeric ratio (anti/syn).Crude product was filtered through a short silica column before the enantiomeric excess was determined using HPLC (ChiralPak IA, 90/10 hexane/isopropanol, 1.0 mL/min, major enantiomer t R = 21.7 min, minor enantiomer t R = 15.9 min).
The catalyst loading in usual reactions (i.e. 1 mol% catalyst = 0.498 mg catalyst) was determined using the concentration of catalyst in the nanogel solution, assuming 100% incorporation of the catalyst in the polymerization.
For reactions where the same number of nanoreactors was used, the same volume of nanogel (2.5 mL) and amount of reagents (38 mg of 4-nitrobenzaldehyde and 0.104 mL of cyclohexanone) were used in each of the reactions.The catalyst loading in each reaction (mol% catalyst) was determined using the method described above and therefore, to give an example, in a reaction using nanogels with catalyst concentration of 1.7 mg/mL 4.25 mg of catalyst was used, which makes the catalyst loading 8.5 mol%.

Encapsulation experiments with Nile Red
Nile red (1.0 mg, 3.14 × 10 -3 mmol) was dissolved in cyclohexanone (0.208 µL, 2.65 mmol) and split into 5 separate vials.To each vial a dispersion of nanogels in water (1.0 mL each) was added with varying DoFs and CLD.The nanogel dispersions were sonicated for 5 minutes, prior to stirring for 24 hours.Then, a small aliquot (0.05 mL) was taken and diluted with water (0.5 mL).Prior to analysis by fluorescence spectroscopy, each sample was filtered through a 0.45 µm syringe filter to remove any precipitated dye.

Determination of the monomer reactivity in water
Due to the different types of polymerization that MMA and ProMA undergo in water in the presence of a water soluble radical initiator (emulsion and precipitation respectfully), the conversion of the monomers was followed by 1 H NMR spectroscopy.A typical nanogel synthesis reaction was set up in the absence of the cross-linker (EGDMA).At predetermined time intervals 10 mL of the reaction mixture were withdrawn with a plastic syringe, dried and analyzed.

Fig S1.
The copolymerization progress of L-proline functionalized methacrylate (15 wt%) and MMA was followed by 1 H NMR spectroscopy where the polymerization starts at the same time with functional L-proline monomer polymerizing slightly faster than MMA.

Control experiments
Control experiments using unfunctionalized PMMA nanogels (24 nm and PD 0.120) were carried out to ensure no background reactions were occurring simply due to the effective concentration of the two reagents within the hydrophobic core.In the absence of tethered catalyst (Entry 1), no reaction was observed and, even upon the addition of unsupported L-proline to the unfunctionalized PMMA nanogels (Entry 2), still no reaction was found, likely due to the high solubility of the catalyst in the surrounding water, essentially resulting in the segregation of catalyst and reagents.This emphasizes the importance of having the catalyst tethered within the particles bringing reaction components with different solubilities together within the same reaction sphere.

Fig S13.
Reaction conversion after 24 hours determined by 1 H NMR spectroscopy, catalyzed by a range of nanogels presented in order of increasing number of pendant methyl groups on the non-functional co-monomer (i.e.methyl, ethyl, n butyl, t butyl (in red) and lauryl).

Fig S4 .Fig S5 .
Fig S4.Effect of degree of catalyst functionalization (DoF) on conversion for reactions carried out with 1 mol% catalyst loading at room temperature after 24 hours for nanogels with varying CLD across the series shown.

Fig S7 .
Fig S7.Aldol reaction carried out using the same number of PMMA nanoreactors (resulting in variable amounts of catalyst: 1-8.5 mol%), the catalyst efficiency is represented by TON.3
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Table S2 .
Aldol reactions carried out in the presence of unfunctionalized PMMA nanogels with and without unsupported L-proline.