Supporting Information. Transformable Materials: Structurally Tailored and. Engineered Macromolecular (STEM) Gels by

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1 Supporting Information Transformable Materials: Structurally Tailored and Engineered Macromolecular (STEM) Gels by Controlled Radical Polymerization Julia Cuthbert a, Antoine Beziau a, Eric Gottlieb a, Liye Fu a, Rui Yuan a, Anna C. Balazs b *, Tomasz Kowalewski a *, Krzysztof Matyjaszewski a * a Department of Chemistry, Center for Macromolecular Engineering, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA b Chemical Engineering Department, University of Pittsburgh, Pittsburgh, PA 15261, USA * Corresponding authors km3b@andrew.cmu.edu tomek@andrew.cmu.edu balazs@pitt.edu HEMA-iBBr, Inimer Synthesis 2-Hydroxyethyl methacrylate (HEMA, 3.00 g, mmol) and triethylamine (11.66 g, mmol) were mixed in 250 ml of DCM in a 500 ml round bottom flask in ice bath. Then nitrogen was bubbled into the flask for 20 minutes to remove oxygen. The mixture was then added by α-bromoisobutyryl bromide (5.57 g, mmol) drop-wise via syringe pump. The reaction S1

2 mixture was then brought to room temperature and stirred for 17 h. After completion of reaction the solvent and extra triethylamine was removed by evaporation under reduced pressure. Ethyl acetate was added into the concentrated mixture and white precipitation was formed and separated by gravitational filtration. The filtrate was then washed with brine and dried with anhydrous MgSO4 and the solvent was removed under reduced pressure yielding 5.43 g of HEMA-iBBr (84 % yield). The final compound was analyzed by 1 H-NMR: (300 MHz, chloroform-d) δ 6.14 (td, J = 2.4, 2.0, 1.2 Hz, 1H), 5.59 (q, J = 1.6 Hz, 1H), (m, 4H), (m, 3H), 1.94 (s, 6H). Figure S 1. The 1 H NMR spectrum of the purified HEMA-iBBr with peak assignments. Linear Models of the STEM-0 Gels Two linear models were synthesized: one without and with inimer, HEMA-iBBr. To a 10 ml Schlenk flask, BMA (2.55 g, 18 mmol, 250 eq), CPADB (0.50 ml of stock 40 mg/ml CPADB in DMF, 0.02 g, 0.07 mmol, 1 eq), and toluene (2.8 ml) were added. To the inimer linear model, HEMA-iBBr (0.20 g, 0.7 mmol, 10 eq) was added. The solutions were degassed by N2 sparging for 30 min. V-70 ( g, 0.18 mmol, 0.25 eq) was added to the solution under positive nitrogen pressure. The reaction was heated at 46ºC and was followed by 1 H NMR and GPC. S2

3 Conversion Conversion A B 30k M n M n, theo 25k M w /M n C 1h 2h 4h 22h M n 20k 15k 10k M w /M n 0.2 5k Time (h) Time (h) Time (h) D BMA Inimer E 30k 25k M n M n, theo M w /M n F 1h 2h 4h 22h M n 20k 15k 10k M w /M n 0.2 5k Time (h) Time (h) Time (h) Figure S 2. The results of the linear models. For BMA monomer only, the conversion was followed by 1 H NMR (A), the dispersity and Mn by GRP (B) in THF, and the GPC traces are shown (C). For the BMA plus inimer model, the conversion was followed by 1 H NMR (D), the dispersity and Mn by GRP (E) in THF, and the GPC traces are shown (F). STEM-0 Synthesis RAFT B15 The STEM gel was prepared from a solution containing BMA (5.72 g, 40 mmol, 75 eq), HEMA-iBBr (0.154 g, 54 mmol, 1 eq), PEO750DMA (2.00 g, 2.7 mmol, 5 eq), CPADB (0.150 g, 0.54 mmol, 1 eq), DMF (0.2 ml), and toluene (5.7 ml). The solution was bubbled under N2 (g) for 15 minutes in an ice bath and stirred. V-70 (0.047 g, 0.10 mmol, 0.25 eq) was added to the solution and the solution was degassed for a further 10 minutes. Using a purged syringe, the solution was injected in a mold composed of two glass plates and a rubber seal that had be previously degassed under N2 (g) for 20 minutes. The mold was placed inside two plastic bags, which were then vacuum sealed. The mold was heated at 46ºC for 3 days in a water bath. The conversion of the BMA and HEMA-iBBr was determined by 1 H NMR characterization (Conv. = 84%). The ratio of reactants was [BMA]/[PEO750DMA]/[CPADB]/[HEMA-iBBr]/[V-70] = [75]/[5]/[1]/[1]/[0.25]; VM:VS = 1:1 in toluene. S3

4 FRP B15 The STEM gel was prepared from a solution containing BMA (2.39 g, 19 mmol, 75 eq), HEMA-iBBr (0.070 g, 0.25 mmol, 1 eq), PEO750DMA ( g, 1.25 mmol, 5eq), DMF (0.2 ml), and toluene (2.4 ml). The solution was bubbled under N2 (g) for 15 minutes in an ice bath and stirred. V-70 (0.019 g, mmol, 0.25 eq) was added to the solution and the solution was degassed for a further 10 minutes. Using a purged syringe, the solution was injected in a mold composed of two glass plates and a rubber seal that had be previously degassed under N2 (g) for 20 minutes. The mold was placed inside two plastic bags, which were then vacuum sealed. The mold was heated at 46ºC for 3 days in a water bath. The conversion of the BMA and HEMA-iBBr was determined by 1 H NMR characterization (Conv. = 99%). The ratio of reactants was [BMA]/[PEO750DMA]/[HEMA-iBBr]/[V-70] = [75]/[5]/[1]/[0.25]; VM:VS = 1:1 in toluene. RAFT B80 The STEM gel was prepared from a solution containing BMA (3.20 g, 23 mmol, 250 eq), HEMA-iBBr (0.25 g, 0.90 mmol, 10 eq), PEO750DMA (0.23 g, 0.30 mmol, 3 eq), CPADB (0.025g, 0.09 mmol, 1 eq), DMF (0.2 ml), and toluene (2.8 ml). The solution was bubbled under N2 (g) for 15 minutes in an ice bath and stirred. V-70 (0.0092g, mmol, 0.3 eq) was added to the solution and the solution was degassed for a further 10 minutes. Using a purged syringe, the solution was injected in a mold composed of two glass plates and a rubber seal that had be previously degassed under N2 (g) for 20 minutes. The mold was placed inside two plastic bags, which were then vacuum sealed. The mold was heated at 46ºC for 3 days in a water bath. The conversion of the BMA and HEMA-iBBr was determined by 1 H NMR characterization (Conv. = 83%). The ratio of reactants was [BMA]/[ PEO750DMA]/[CPADB]/[HEMA-iBBr]/[V-70] = [75]/[1]/[0.3]/[3]/[0.1]; VM:VS = 1:1 in toluene. RAFT B40 The STEM gel was prepared from a solution containing BMA (3.17 g, 22 mmol, 122 eq), HEMA-iBBr (0.49 g, 1.8 mmol, 10 eq), PEO750DMA (0.40 g, 0.54 mmol, 3 eq), CPADB (0.051g, mmol, 1 eq), DMF (0.2 ml), and toluene (2.8 ml). The solution was bubbled under N2 (g) for 15 minutes in an ice bath and stirred. V-70 (0.056 g, mmol, 0.1 eq) was added to the solution and the solution was degassed for a further 10 minutes. Using a purged syringe, the S4

5 solution was injected in a mold composed of two glass plates and a rubber seal that had be previously degassed under N2 (g) for 20 minutes. The mold was placed inside two plastic bags, which were then vacuum sealed. The mold was heated at 46ºC for 3 days in a water bath. The conversion of the BMA and HEMA-iBBr was determined by 1 H NMR characterization (Conv. = 67.5%). The ratio of reactants was [BMA]/[PEO750DMA]/[CPADB]/[HEMA-iBBr]/[V-70] = [122]/[3]/[1]/[10]/[0.1]; VM:VS = 1:1 in toluene. RAFT M80 (CPADB as RAFT agent) The STEM gel was prepared from a solution containing MEO2MA (3.37 g, 18 mmol, 250 eq), HEMA-iBBr (0.200 g, 0.72 mmol, 10 eq), PEO750DMA (0.23 g, 0.20 mmol, 3 eq), CPADB (0.020g, mmol, 1 eq), DMF (0.2 ml), and toluene (3.4 ml). The solution was bubbled under N2 (g) for 20 minutes in an ice bath and stirred. V-70 (0.066 g, mmol, 0.3 eq) was added to the solution and the solution was degassed for a further 10 minutes. Using a purged syringe, the solution was transferred to a mold composed of two glass plates and a rubber seal that had be previously degassed under N2 (g) for 20 minutes. The mold was placed inside two plastic bags, which were then vacuum sealed. The mold was heated at 46ºC for 3 days in a water bath. The conversion of the MEO2MA and HEMA-iBBr was determined by 1 H NMR characterization (Conv. = 46%). The ratio of reactants was [BMA]/[PEODMA750]/[CPADB]/[HEMA-iBBr]/[V- 70] = [122]/[3]/[1]/[10]/[0.1]; VM:VS = 1:1 in toluene. RAFT M80 (CDTP as RAFT agent) The STEM gel was prepared from a solution containing MEO2MA (2.73 g, 14 mmol, 250 eq), HEMA-iBBr (0.16 g, 0.57 mmol, 10 eq), PEO750DMA (0.23 g, 0.20 mmol, 3 eq), CDTP (0.020g, mmol, 1 eq), DMF (0.2 ml), and toluene (2.2 ml). The solution was bubbled under N2 (g) for 20 minutes in an ice bath and stirred. V-70 (10 mg/ml stock solution in DMF, ml, mmol, 0.3 eq) was added to the solution and the solution was degassed for a further 10 minutes. Using a purged syringe, the solution was transferred to a mold composed of two glass plates and a rubber seal that had be previously degassed under N2 (g) for 20 minutes. The mold was placed inside two plastic bags, which were then vacuum sealed. The mold was heated at 46ºC for 3 days in a water bath. The conversion of the MEO2MA and HEMA-iBBr was determined by S5

6 1 H NMR characterization (Conv. = 46%). The ratio of reactants was [BMA]/[ PEO750DMA]/[CPADB]/[HEMA-iBBr]/[V-70] = [122]/[3]/[1]/[10]/[0.1]; VM:VS = 1:1 in toluene. Table S 1. The theoretical molecular weight of the STEM-0 Gel repeat units and inimer per repeat. STEM-0 Gel MW(Theo) Repeat Unit Inimer per Repeat RAFT B FRP B RAFT B RAFT B RAFT M80 (CPADB as RAFT agent) RAFT M80 (CDTP as RAFT agent Reaction of Irgacure Generated Radicals with Copper Catalyst Scheme S 1. The decomposition of the photo-active Irga-MA inimer when exposed to UV light. An acyl and isopropanol radical are generated. In an NMR tube, a solution containing monomer, Irga-MA inimer, and CuBr2/TPMA in d6-dmso was prepared. [MMA]/[Irga-MA]/[CuBr2(TPMA)] = 200/1/2. Four solutions were prepared with different CuBr2 concentrations: 0 mm, 4 mm, 10 mm, 20 mm. The solutions were irradiated for 12 h and the decomposition of inimer (seen in S6

7 Decomposition (%) the appearance of acyl radical peaks) was followed by 1 H NMR (Figure S 3). Copper catalyst substantially decreased the reaction efficiency. 100% 80% 60% 20 mm 10 mm 4 mm 0 mm 40% 20% 0% Irradiation time (h) Figure S 3. The decomposition of photo-active IrgaMA inimer followed by 1 H NMR in solutions varying the Cu(II) concentrations: 0 mm (diamonds, purple), 4 mm (squares, blue), 10 mm (triangles, green), and 20 mm (circles, red). S7

8 Figure S 4. Presence of acyl radicals in the absence and presence of Cu(II). Top: Irgacure 2959 before irradiation. Middle: After 6 h irradiation in the absence of Cu(II). Bottom: After 6 h irradiation in the presence of Cu(II). Scheme S 2. Proposed mechanism for the formation of ATRP inactive species in the presence of Cu(II). S8

9 Gelation Comparison: FRP vs RAFT Polymerization The synthesis of the FRP and RAFT polymerization gels was performed as described previous for the STEM-0 gels until after sparging with N2. The pre-gel solutions were as follows: FRP: [BMA]/[crosslinker]/[inimer]/[rad.in] = [1000]/[3]/[10]/[0.4] VS = VM in toluene. RAFT: [BMA]/[crosslinker]/[inimer]/[CPADB]/[rad.in] = [1000]/[3]/[10]/[1]/[0.4] VS = VM in toluene. The degassed pre-gel solutions were added to degassed 5 ml glass vials and heated at 46 C on a heating mantle. The gelation followed by 1 H NMR, GPC, and visual observation (Figure S 5). When the solution became sufficiently viscous, sampling was stopped. The gel point was observed visually and the reactions were stopped after 18h. Conversion of the final gels was determined by extraction of unreacted monomer in CDCl3 by 1 H NMR. As expected, the FRP gel reached its gelation point before the RAFT gel. S9

10 Conversion Conversion A Gel B 20 min 30 min 60 min 90 min Time (min) E7 Molecular Weight C Gel D 1.5h 4h 5h 6h Time (min) E7 Molecular Weight Figure S 5. Gelation of the FRP and RAFT formulations. The FRP conversion was followed by 1 H NMR (A) and GPC (B). The RAFT conversion was also followed by 1 H NMR (C) and GPC (D). The grey areas of A and C indicate the visual gel point (time at which the gel did not flow when the vial was inverted, see inset C). STEM Gel Post-Synthesis Modifications by Photo ATRP RAFT B75 Grafting from DMAEMA Side Chains The dried STEM-0 gels, RAFT B15 and FRP B15, were weighted and swollen in an infiltration solution containing the secondary monomer, catalyst (CuBr2/Me6TREN), and solvent (DMF) overnight (24 h) (Table S 2). The equivalents were [DMAEMA]/[inimer]/[CuBr2]/[Me6TREN] = [100]/[1]/[0.09]/[0.54]; VM:VS = 1:3 in DMF. The swollen STEM gels were weighted to determine equivalent monomer infiltrated and placed in a mold. The mold covered and degassed under nitrogen for 20 min and then irradiated with UV lamp S10

11 Swelling Ratio (%) (365 nm, 5 mw/cm 2 ) for 4 h. Small pieces of a swollen gels were immersed in CDCl3 and vortexed to extract unreacted secondary monomer before and after UV irradiation. The monomer conversion was determined by 1 H NMR. Table S 2.Infiltration solution composition and modifications to RAFT B15 and to FRP B15. STEM-0 Label Gel Monomer Monomer Eq Conv Infiltrated Monomer DP (Theo) side chains RAFT B15_D DMAEMA % 35 FRP B15_D DMAEMA 37 88% Mother STEM Gels Daughter STEM Gels RAFT_B15 FRP_B15 RAFT_B15_D FRP_B15_D Gel Figure S 6. Swelling ratios of STEM-0 RAFT B15 and FRP B15 and STEM-1 gels with grafted PDMAEMA side chains (RAFT B15_D/FRP B15_D) in water. Temporal Control Over Side Chain Growth by ATRP The same procedure to graft the PBMA side chains was followed as described previously. The pristine B80 was swollen in a solution containing BMA, catalyst, and solvent. The swelling solution composition was: [BMA]/[inimer]/[CuBr2]/[Me6TREN] = [200]/[1]/[0.09]/[0.54]; VM:VS = 1:1 in DMF. The 62 equivalents BMA were swollen into the gel. The B80were irradiated from h and conversion was determined by 1 H NMR (Table S 3). S11

12 Table S 3. Conversion, DP, and theoretical Mn of the PBMA side chains grown from B80 by photo ATRP. Time (h) Conversion (%) DP Mn (Theo) 0 0% % % % % In a 20 ml glass vial, the following solution was prepared: [BMA]/[EBiB]/[CuBr2]/[Me6TREN] = [275]/[1]/[0.09]/[0.54]; VM:VS = 1:1 in DMF. The solution was degassed under nitrogen for 20 min and irradiated under UV for 8 h. The reaction was followed 1 H NMR and GPC (Table S 4, Figure S 7). Table S 4. Solution polymerization for comparison to grafting from the inimers. Time (h) Conv. ( 1 H NMR)Mn (Theo) DP (Theo) Mn (GPC) Ð % % % % % % S12

13 0.25h 0.75h 1.5h 3h 4h 8h Molecular Weight Figure S 7. GPC traces for the BMA solution polymerization by photo ATRP related to Table S 4. Side Chains STEM-1 Procedure: Modifying B40 and B80 with PDMAEMA, PHEMA, and PBA The same general procedure was followed as described previously. The composition of the swelling solutions is described in Table S 5. Table S 5. Swelling solution composition for the PDMAEMA and PHEMA modified STEM gels. STEM-1 Gel Label Side Monomer Chain Swelling Soln Monomer Monomer Eq. Infiltrated Eq VM:VS B40_D DMAEMA :2 B40_B BA :2 B80_D DMAEMA :2 B80_BM BMA :1 B80_H HEMA :2 B80_DH DMAEMA & HEMA 100 & & 22 1:1 B80_B BA :2 *In all cases: inimer = 1 eq and CuBr2/Me6TREN = 0.09/0.54 eq. Solvent = DMF. Swelling Ratios S13

14 G'/G'' (Pa) G'/G'' (Pa) Swelling Ratio 14 B 80 _D B 40 _D B 80 _H B 80 _DH ºC 30ºC 35ºC 40ºC 45ºC 50ºC 60ºC Temperature ( O C) Figure S 8. Swelling ratios of the PDMAEMA and PHEMA grafted STEM-1 gels in Tris/HCl buffer (ph=4) from 25 C to 60 C. The range of the three values is the uncertainty G' G'' B 40 G' G'' B 40 _D G' G'' B 40 _BA Freq (rad/s) 10 6 G' G'' B 80 G' G'' B 80 _D 10 5 G' G'' B 80 _H G' G'' B 80 _DH G' G'' B 80 _B Freq (rad/s) Figure S 9. Frequency sweeps on the STEM-0 B80 and corresponding STEM-1 gels with PDMAEMA, PHEMA, and PBA. The measurements were performed at room temperature (T=22 C) and at a constant strain = 0.1%. S14

15 G'/G'' (Pa) G'/G'' (Pa) Tan ( ) 10 9 A G' G'' B80 _BM B G' G'' B80 _BM Freq (rad/s) Temperature ( O C) Figure S 10. Storage (G ) and loss (G ) modulus dependence on frequency (A) and dependence on temperature (B), including tan (δ) Ffor B80 grafted with PBMA side chains,. The frequency sweep measurement was performed at room temperature (T=22 C) and at a constant strain = 0.1%. The measurement was performed using a constant ω = 6.28 rad/s (1 Hz) and at a constant strain = 0.1%. Figure S 11. Single-piece amphiphilic STEM gel by grafting one half with PDMAEMA side chains. Initial pink color is due to the presence of the RAFT agent, CPADB. S15

16 Stess (, MPa) Shear Modulus G* (Pa) Tan ( ) 10 8 G* Pristine M 80 G* Irradiated Gel 10 7 G* Covered Gel Freq (rad/s) Figure S 12. Effect of PMMA side chains grafted from the network compared to the pristine and covered M80. The shear modulus (G*) vs frequency (rad/s) for pristine M80 (black), covered half (red) and irradiated half containing PMMA side chains (blue) are shown in closed symbols. The tan (δ) values are shown in open diamond symbols ( ) T =22ºC; strain =0.1%. 3 Pristine M 80 Covered PMMA side chains 2 E = 13.7 MPa 1 E = 1.3 MPa E = 1.4 MPa Strain Figure S 13. Effect of grafting PMMA side chains from the network and the covered area of the flap STEM-1 gel. Stress (σ, MPa) vs. strain (ε) traces acquired in compressibility tests are shown in the form of black open symbols corresponding respectively to pristine M80 (Δ), covered half of the flap STEM gel ( ), PMMA graft half of the flap STEM-1 gel ( ). Dashed lines and red symbols correspond to the linear fits to experimental data. The slopes of fitted curves, which correspond to the values of Young's Modulus E (MPa) are shown in boxes located next to respective curves. S16

17 Dual Grafted STEM-1 Gel The M80 STEM-0 gel was placed in a vial. To the vial, a solution containing DMAEMA and catalyst in water was added. Then, the toluene layer containing BMA and catalyst was added on top (Table S 6). Both solutions were prepared in large excess to fully immerse the gel in two layers. The gel was swollen overnight (24 h). The infiltrated gel was placed in a mold, covered and degassed under nitrogen for 20 min (Figure S 14). The gel was irradiated for 4 h, washed and dried as described previously. By gravimetry, the percent by weight PDMAEMA and PBMA side chains = 36%. Table S 6. Swelling solution conditions for the dual grafted M80 STEM-1 gel Solution Solvent Monomer Monomer Conc [M] CuBr2 (mm) Me6TREN (mm) VS:VM Toluene BMA :1 Water DMAEMA :1 Figure S 14. Experimental procedure for dual grafting different monomers from the STEM-0 gels. The STEM gel was swollen in immiscible solutions: bottom containing DMAEMA and catalyst in water and top containing BMA and catalyst in toluene. The swollen gel was placed in a sealed mold, degassed, and irradiated. The result was different polymer side chains grafted from two halves of the same material. S17

18 G'/G'' (Pa) Swelling Ratio Tan ( ) G'/G'' (Pa) Tan (delta) M 80 in water at room temperature Figure S 15. Swelling ratio of M80 at room temperature (T=22 C) in water. RAFT M80 (CDTP as RAFT agent) 10 9 a) G' 10 8 G'' Tan ( ) b) 10 9 G' G'' 10 8 Tan delta Freq (rad/s) Temp ( o C) 0 Figure S 16. Frequency sweeps of the pristine M80 (a). The measurement was performed at room temperature (T=22 C) and at a constant strain = 0.1%. The temperature sweep of pristine material (b). The measurement was performed using a constant ω = 6.28 rad/s (1 Hz) and at a constant strain = 0.1%. S18