S1 Supporting Information for Poly(allyl alcohol) Homo- and Block Polymers by Postpolymerization Reduction of an Activated Polyacrylamide Michael B. Larsen, Shao-Jie Wang, and Marc A. Hillmyer * Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 Wanhua Chemical Group Co., Ltd., Yantai, Shandong Province, P.R. China 264002 Materials. Unless otherwise noted, all reagents were purchased from commercial sources and used as received. Styrene (99%), N,N-dimethylacrylamide (99%), and tert-butyl acrylate (98%) were passed through a plug of basic alumina to remove inhibitor prior to use. S-Dodecyl-S -(α,α - dimethyl-α -acetic acid) trithiocarbonate (DDMAT) was synthesized as previously reported. 1 di- Boc acrylamide (DBAm) was synthesized as previously reported and recrystallized twice from 10% H2O/EtOH prior to use. 2 Tetrahydrofuran, toluene, diethyl ether, and dichloromethane were purified on a home-built solvent purification system. Instrumentation. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. NMR spectra were recorded on a Bruker Avance III HD 500 MHz spectrometer. Chemical shifts are reported in δ units, expressed in ppm downfield from tetramethylsilane using the residual protiosolvent as an internal standard ( 1 H: CDCl3, 7.26 ppm; CD3OD, 3.31 ppm; DMF-d7, 8.03 ppm. 13 C: CD3OD, 49.3 ppm). Size exclusion chromatography (SEC) was performed in either 1) DMF containing 0.05 M LiBr (50 C, 1 ml/min) on an Agilent Infinity 1200 HPLC system equipped with two Viscotek I-MBMMW-3078 columns, a Wyatt HELEOS-II multi-angle laser light scattering detector, and a Wyatt Optilab T-rEX differential refractive index detector; or 2) water containing 0.1 M Na2SO4 and 1 wt% acetic acid (25 C, 0.4 ml/min) on an Agilent Infinity 1260 HPLC system equipped with Eprogen CATSEC100, CATSEC300, and CATSEC1000 columns, a Wyatt HELEOS-II multi-angle laser light scattering detector, and a Wyatt Optilab T-rEX differential refractive index detector. Mass spectrometry analysis was performed at The University of Minnesota Department of Chemistry Mass Spectrometry Laboratory (MSL), supported by the Office of the Vice President of Research, College of Science and Engineering, and the Department of Chemistry at the University of Minnesota, as well as The National Science Foundation (NSF
S2 Award CHE-1336940). The content of this paper is the sole responsibility of the authors and does not represent endorsement by the MSL or NSF. MALDI-MS spectra were recorded on an Applied Biosystems Sciex-4800 MALDI/TOF/TOF-MS spectrometer in reflectron mode; 2,5- dihydroxybenzoic acid was used as the matrix. FTIR spectra were recorded on a Bruker Alpha Platinum ATR spectrometer. Differential scanning calorimetry (DSC) analyses were performed on a TA Instruments Discovery DSC using hermetically-sealed aluminum T-zero pans. Scans were conducted under nitrogen atmosphere at a heating rate of 10 C/min unless otherwise noted. Thermogravimetric analyses (TGA) were performed on a TA Instruments Q500 under nitrogen atmosphere at a heating rate of 10 C/min. Scattering experiments were performed using X-rays of wavelength 0.729 Å, and the scattering intensity was collected on a 2D Mar CCD detector at room temperature with a sample-to-detector distance of 850 cm. Intensity as a function of the wavevector (q), where q = (4π/λ) sin(θ/2), was obtained by azimuthal integration of the 2D patterns. This scattering work was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Data was collected using an instrument funded by the National Science Foundation under Award Number 0960140. AFM imaging was performed in tapping mode on a Bruker Nanoscope V Multimode 8; samples were spin coated from 1 wt% solutions in DMF at 2000 rpm. UV photopolymerizations were performed using a MelodySusie UV Gel Nail Polish Dryer (36 W, model DR-301C) as UV source. Visible light photopolymerizations were performed using a homebuilt LED photoreactor, constructed according to previous reports; 3 briefly, a strip of commercial blue LED lights (λmax = 455 nm; 12V DC source) were wound around the inside of a foil-covered beaker. Due to the homemade nature of the reactor, power density within the beaker exhibited angular dependence; a range of 27 42 mw/cm 2 was measured. The midpoint of the range (35 mw/cm 2 ) is used as the power density in the main text. To prevent warming inside the photoreactor, airflow in and out of the beaker was continuously maintained for the duration of the polymerization.
S3 Exploration of conditions for synthesis of high Mn PDBAm. As discussed in the main text, the reduction of PDBAm to PAA results in a theoretical Mn reduction of 79%. As a stated goal of our work was the synthesis of high Mn PAA, we explored a variety of conditions for synthesis of high Mn PDBAm precursor (main text Scheme 1 and Table 1); representative examples of each synthetic procedure are given below. Free-radical UV photopolymerization of DBAm (A). DBAm (2.0 g, 7.4 mmol, 200 equiv) was melted in a vial by heating to 80 C. While molten, 2,2-dimethoxy-2-phenylacetophenone (DMPA) (9.4 mg, 0.4 mmol, 1 equiv) was added. After the solution became homogenous it was poured into a glass Petri dish preheated to 70 C on a hot plate, and the UV source was turned on and placed on top of the hot plate. After 1.5 h the UV source was removed and a sample of the was taken to analyze conversion by 1 H NMR (84%), after which the polymer was cooled to room temperature, dissolved in acetone, and precipitated in 10% H2O/MeOH (v/v). The polymer was filtered and dried under vacuum at 65 C (1.45 g, 86% based on conversion; Mn 1.5 MDa, Mw 2.6 MDa, Ð 1.7). Free-radical polymerization of DBAm (B). DBAm (4.0 g, 14.7 mmol, 100 equiv) and AIBN (24 mg, 0.15 mmol, 1 equiv) were dissolved in THF (2.67 ml) and the solution was degassed via three freeze-pump-thaw cycles. The flask was backfilled with Ar and stirred at 80 C. After 2 h the solution was cooled, opened to air, and diluted with THF. The polymer was precipitated in 10% H2O/MeOH (v/v), collected, redissolved in THF, and reprecipitated in 10% H2O/MeOH. The polymer was filtered and dried under vacuum at 65 C (2.28 g, 57%; Mn 29 kda, Mw 47 kda, Ð 1.6). RAFT polymerization of DBAm (C). DBAm (2.0 g, 7.4 mmol, 480 equiv.), DDMAT (5.6 mg, 0.015 mmol, 1 equiv), and AIBN (0.8 mg, 4.9 10-3 mmol, 0.4 equiv; added as a stock solution in toluene, 20 mg/ml) were dissolved in dioxane (7 ml). The solution was degassed via three freezepump-thaw cycles, backfilled with Ar, and stirred at 60 C. After 22 h the solution was cooled, opened to air, and a sample taken to analyze conversion by 1 H NMR (52%). The solution was precipitated into 10% H2O/MeOH (v/v), filtered, redissolved in THF, and reprecipitated in 10%
S4 H2O/MeOH (v/v). The purified polymer was dried under vacuum at 65 C (596 mg, 57% based on conversion; Mn 66 kda, Mw 93 kda, Ð 1.4). Visible light mediated controlled radical polymerization (D). DBAm (500 mg, 1.84 mmol, 375 equiv) and DDMAT (1.8 mg, 4.9 10-3 mmol, 1 equiv) were dissolved in dioxane (0.25 ml; required gentle heating for full homogeneity). The solution was degassed via three freeze-pumpthaw cycles, backfilled with Ar, and placed in the LED photoreactor on a stirplate. The solution was stirred, the LEDs were turned on, and airflow through the reactor was started. At 16 h (NOTE: prolonging reaction time beyond 16 h led to significant increases in dispersity and/or bimodal molar mass distributions) the LEDs were turned off, the reaction opened to air, and a sample taken to check conversion by 1 H NMR (> 95%). The polymer was dissolved in acetone and precipitated in 10% H2O/MeOH (v/v), filtered, and dried under vacuum at 65 C (452 mg, 90% based on full conversion; Mn 152 kda, Mw 253 kda, Ð 1.5). General procedure for reduction of PDBAm to PAA. PDBAm (400 mg, 1.47 mmol repeat unit, 1 equiv) was dissolved in absolute EtOH (5 ml). NaBH4 (139 mg, 3.69 mmol, 2.5 equiv) was added in one portion, along with a septum with a vent needle. The reaction was stirred under ambient conditions for 18 h, during which time a significant amount of white solids precipitated. Acetone (5 ml) was added to fully precipitate the polymer and consume any residual NaBH4, and the polymer was filtered and redissolved in MeOH. The MeOH solution was passed through a 0.45 μm syringe filter, and acetone was added to the filtrate to precipitate the polymer. The purified polymer was filtered and dried under vacuum at 65 C for at least 48 h (68 mg, 81%; Mn NMR 30 kda, Mn SEC 41 kda, Mw SEC 43 kda, Ð 1.1) Synthesis of PAA block polymers was largely the same; however, solubility issues complicated precipitation and purification. Deviations from the above procedure for each block polymer are noted below: PAA-b-PDMAm: used 2:1 hexanes:acetone (v/v) for precipitation PAA-b-PtBuAc: used 2:1 pentane:acetone (v/v) for precipitation PS-b-PAA: used DMF as solvent for reduction, and purified after first precipitation via Soxhlet extraction with acetone.
S5 General procedure for synthesis of block polymers. Block polymers were prepared by visible light-mediated controlled radical polymerization, using either 1) DDMAT as photoiniferter and preparing both blocks in one pot, or 2) using a trithiocarbonate-functionalized macro-cta as photoiniferter. One-pot polymerization, DDMAT as photoiniferter: DBAm (500 mg, 1.84 mmol, 37.5 equiv) and DDMAT (17.9 mg, 0.049 mmol, 1 equiv) were dissolved in dioxane (0.25 ml, required gentle heating for full homogeneity). The solution was degassed via three freeze-pump-thaw cycles, backfilled with Ar, and placed in the LED photoreactor on a stirplate. The stirring and LEDs were turned on and airflow through the reactor was started. At 16 h (NOTE: prolonging reaction time beyond 16 h led to significant increases in dispersity and/or bimodal molar mass distributions) the LEDs were turned off, the reaction opened to air, and a sample taken to check conversion by 1 H NMR (> 95%) and molar mass by SEC (Mn 12 kda, Mw 15 kda, Ð 1.2). Into the same reaction vessel, DMAm (0.19 ml, 1.84 mmol, 37.5 equiv) was added and the solution vortexed to homogeneity. The solution was degassed via three freeze-pump-thaw cycles, backfilled with Ar, and placed back in the LED photoreactor on a stirplate. The stirring and LEDs were turned on and airflow through the reactor was started. At 16 h the LEDs were turned off, the reaction was opened to air, diluted with acetone, and precipitated in cold pentane. The polymer was collected and dried under vacuum at 65 C (466 mg, 68% based on full conversion of both blocks; Mn 15 kda, Mw 18 kda, Ð 1.2). PDBAm-b-tBuAc was made in an identical manner, substituting tbuac for DMAm. Macro-CTA as photoiniferter: Styrene (2 ml, 17.4 mmol, 75 equiv), DDMAT (84.4 mg, 0.23 mmol, 1 equiv), and AIBN (9.6 mg, 0.058 mmol, 0.25 equiv) were dissolved in toluene (2 ml). The solution was degassed via three freeze-pump-thaw cycles, backfilled with Ar, and stirred at 110 C. After 24 h the reaction was cooled, precipitated in cold MeOH, and filtered. The purified polymer was dried under vacuum at 80 C (1.21 g, 60%; Mn 5.4 kda, Mw 5.5 kda, Ð 1.01).
S6 The above polystyrene (250 mg, 0.048 mmol CTA chain end, 1 equiv) was dissolved in toluene (0.75 ml) and DBAm (522 mg, 1.92 mmol, 40 equiv) was added (required gentle heating for full homogeneity). The solution was degassed via three freeze-pump-thaw cycles, backfilled with Ar, and placed in the LED photoreactor on a stirplate. The stirring and LEDs were turned on and airflow through the reactor was started. At 17 h the LEDs were turned off and the reaction was opened to air, diluted with acetone, and precipitated in 10% H2O/MeOH (v/v). The purified polymer was collected and dried under vacuum at 75 C (520 mg, 67% based on full conversion of DBAm; Mn 16 kda, Mw 17 kda, Ð 1.06).
S7 Figure S1. 1 H NMR spectrum (CDCl3, 500 MHz) and assignments of PDBAm (Table 1, entry 4). Polymer is too large (Mn,SEC = 152 kda) for identification of endgroups.
S8 * Figure S2. 1 H NMR spectrum (CD3OD, 500 MHz) and assignments of PAA (Table 1, entry 4). * = residual acetone, = CHD2OD, = H2O. Inset: magnification of gem-dimethyl endgroup resonance used for Mn calculation. -OH resonance not visible due to H D exchange with CD3OD.
S9 Figure S3. 1 H 1 H COSY spectrum (CD3OD, 500 MHz) of PAA (Table 1, entry 4). Note coupling of geminal protons in meso dyad (δ = 1.44, 1.16 ppm).
S10 * * Figure S4. 13 C NMR spectrum (CD3OD, 126 MHz) of PAA (Table 1, entry 4). * = residual acetone. Inset: expansion of PAA resonances.
S11 * * Figure S5. 1 H NMR spectra (D2O, ph = 2; 500 MHz) of PAA upon dissolution (top) and after 5 days of exposure to acidic conditions (bottom). * = residual acetone. ph was adjusted by addition of trifluoroacetic acid.
S12 Figure S6. 1 H NMR spectra (D2O, ph = 12; 500 MHz) of PAA upon dissolution (top) and after 5 days of exposure to basic conditions (bottom). ph was adjusted by addition of NaOH.
S13 a) b) 1000 2000 3000 4000 5000 6000 mass (m/z) 58.0 58.0 58.0 3000 3200 3400 3600 3800 mass (m/z) Figure S7. a) Full MALDI spectrum of PAA (Table 1, entry 6). b) Assignment of populations of PAA with different endgroups. Primary population (black) is as anticipated from reduction of DDMAT endgroups with NaBH4; secondary (red) results from reaction of isopropanol (produced in NaBH4 reduction) with carboxylic acid endgroup; and tertiary (blue) results from reaction with
transmittance transmittance S14 ethanol (solvent for reduction). Calculated and observed m/z values are those of the leftmost peak (lower m/z) bracketed for each series. 3500 3000 2500 2000 1500 1000 500 1.0 0.9 0.8 0.7 0.6 0.9 0.8 0.7 3500 3000 2500 2000 1500 1000 500 wavenumbers (cm -1 ) Figure S8. ATR-IR spectra of PDBAm (top) and PAA (bottom). Note disappearance of DBAm carbonyl stretching frequencies centered at ca. 1750 cm -1 and appearance of O-H stretch in PAA at 3250 cm -1.
% mass heat flow (endo up) S15 1st cool 2nd heat 2nd cool 3rd heat 0.2 W/g 25 50 75 100 125 150 175 200 225 250 temperature ( C) Figure S9. DSC thermogram of PAA, 1 st cooling 3 rd heating ramps, 10 C/min; Tg = 53 C. Broad endotherm maximum = 149 C; integration = 20 J/g. 100 80 60 40 20 0 50 100 150 200 250 300 350 400 450 500 550 temperature ( C) Figure S10. TGA thermogram of PAA. Td, 5% = 352 C.
intensity (arbitrary scale) S16 5 10 15 20 25 30 2 (degrees) Figure S11. WAXS pattern of PAA. Sample was annealed at 250 C for 10 min and cooled to room temperature prior to scattering experiment.
normalized dri S17 Table S1. Molar mass information for block polymers 1, 2, and 3. block polymer a Determined by Mn,SEC PDBAm precursor 0.21. b Unable to be determined due to signal overlap in 1 H NMR. A block B block PDBAm precursor Mn, A (kda) NMR/SEC Mn, B (kda) NMR/SEC Ð Mn, PAA theo (kda) a PAA block polymer Mn, PAA (kda) NMR Mn partner (kda) NMR 1 DBAm DMAm 11 / 12 3.3 / 3.4 1.2 2.5 3.5 3.4 2 DBAm tbuac 11 / 20 5.6 / 7.0 1.1 4.0 3.2 6.1 3 S DBAm 6.6 / 5.4 13 / 10 1.1 2.1 b b 14 16 18 20 retention volume (ml) Figure S12. SEC chromatograms of PDBAm (blue; Mn 12 kda, Mw 15 kda, Ð 1.3) and PDBAm-b-PDMAm (blue and black; Mn 15 kda, Mw 18 kda, Ð 1.2).
S18 * Figure S13. 1 H NMR spectra of PDBAm-b-PDMAm (top, CDCl3) and PAA-b-PDMAm (bottom, CD3OD). * = residual MeOH, = CHD2OD, = H2O. Note maintenance of resonances assigned to amidic NMe2 (δ = 2.8 3.25) after reduction.
S19 Figure S14. 13 C NMR spectrum of PAA-b-PDMAm (CD3OD, 126 MHz). Inset: expansion of resonances corresponding to block polymer. Top to bottom: PDMAm carbonyl; PAA sidechain methylene; overlapping PAA + PDMAm backbone and PDMAm amidic methyl groups.
transmittance transmittance S20 1.0 3500 3000 2500 2000 1500 1000 500 0.9 0.8 0.7 0.6 0.5 1.0 0.9 0.8 0.7 3500 3000 2500 2000 1500 1000 500 wavenumbers (cm -1 ) Figure S15. ATR-IR spectra of PDBAm-b-PDMAm (top) and PAA-b-PDMAm (bottom). Note disappearance of DBAm carbonyl stretches centered at ca. 1750 cm -1, while DMAm carbonyl (1620 cm -1 ) is unaffected.
normalized dri S21 14 16 18 20 retention volume (ml) Figure S16. SEC chromatograms of PDBAm (blue; Mn 20 kda, Mw 23 kda, Ð 1.2) and PDBAmb-PtBuAc (blue and black; Mn 27 kda, Mw 30 kda, Ð 1.1).
S22 * Figure S17. 1 H NMR spectra of PDBAm-b-PtBuAc (top, CDCl3) and PAA-b-PDMAm (bottom, CD3OD). * = residual MeOH, = CHD2OD, = H2O. Note maintenance of resonances assigned to OtBu ester (δ = 1.48 ppm) after reduction.
transmittance transmittance S23 3500 3000 2500 2000 1500 1000 500 1.0 0.9 0.8 0.7 1.0 0.9 0.8 0.7 3500 3000 2500 2000 1500 1000 500 wavenumbers (cm -1 ) Figure S18. ATR-IR spectra of PDBAm-b-PtBuAc (top) and PAA-b-PtBuAc (bottom). Note disappearance of DBAm carbonyl stretches centered at ca. 1750 cm -1, while tbuac carbonyl (1725 cm -1 ) is unaffected.
normalized dri S24 14 16 18 20 retention volume (ml) Figure S19. SEC chromatograms of PS (green; Mn 5.4 kda, Mw 5.5 kda, Ð 1.01) and PS-b- PDBAm (green and blue; Mn 16 kda, Mw 17 kda, Ð 1.1).
S25 * Figure S20. 1 H spectra of PS-b-PDBAm (top, CDCl3) and PS-b-PAA (bottom, DMF-d7). PS-b- PAA is only slightly soluble in DMF-d7, resulting in poor shimming and broad signals as a dispersion is formed; additionally, the -CH2OH resonance assigned to the AA repeat unit is obscured by the HOD signal. * = HOD, = DMF-d6, = CHCl3.
heat flow (endo up) transmittance transmittance S26 3500 3000 2500 2000 1500 1000 500 1.0 0.9 0.8 0.7 0.6 1.0 0.9 0.8 0.7 0.6 3500 3000 2500 2000 1500 1000 500 wavenumbers (cm -1 ) Figure S21. ATR-IR spectra of PS-b-PDBAm (top) and PS-b-PAA (bottom). Note disappearance of DBAm carbonyl stretches centered at ca. 1750 cm -1. 0.2 W/g polymer 1 polymer 2 polymer 3 T g 37 C T g 28 C T g 42 C T g 96 C T g 39 C 25 50 75 100 temperature ( C) Figure S22. DSC chromatogram of block polymers 1, 2, and 3. Tg endotherms are indicated in each chromatogram. 2 nd heating ramps, 20 C/min.
S27 a) b) 250 nm 250 nm c) d) 250 nm 250 nm Figure S23. AFM images of as-spun block polymers 3 and 2. (a) Height image of 3; (b) phase image of 3; (c) height image of 2; (d) phase image of 2. PAA is likely the softer block (blue) in each case. Fitting of reflection data by ellipsometry was poor and thus no reliable film thickness information was obtained, but we estimate films to be 30 50 nm thick based on spin coating of similar wt% solutions at the same spin rate.
I (arbitrary log scale) S28 polymer 2 polymer 3 q* 0.40 nm -1 d 16 nm q* 0.42 nm -1 d 15 nm 0.1 1 q (nm -1 ) Figure S24. SAXS data of PAA block polymers. 2 was cast from MeOH and dried under ambient conditions, while 3 was annealed at 250 C for 10 min and cooled to room temperature.
S29 References 1 Touris, A.; Chanpuriya, S.; Hillmyer, M. A.; Bates, F. S. Synthetic strategies for the generation of ABCAʹ type asymmetric tetrablock terpolymers Polym. Chem. 2014, 5, 5551-5559. 2 Larsen, M. B.; Herzog, S. E.; Quilter, H. C.; Hillmyer, M. A. Activated Polyacrylamides as Versatile Substrates for Postpolymerization Modification ACS Macro Lett. 2018, 7, 122-126. 3 McKenzie, T. G.; Fu, Q.; Wong, E. H. H.; Dunstan, D. E.; Qiao, G. G. Visible Light Mediated Controlled Radical Polymerization in the Absence of Exogenous Radical Sources or Catalysts Macromolecules 2015, 48, 3864-3872.