Supporting Information

Oxygen Tolerance in Living Radical Polymerization: Investigation of

Mechanism and Implementation in Continuous Flow Polymerisation

Nathaniel Corrigan,a, b

Dzulfadhli Rosli,a Jesse Warren Jeffery Jones,

a Jiangtao Xu,

a,b* and Cyrille Boyer

a, b*

a- Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, UNSW

Australia, Sydney, NSW 2052, Australia

b- Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia, Sydney,

NSW 2052, Australia

EXPERIMENTAL SECTION

Materials

Methyl acrylate (MA, 99%), N,N’-dimethylacrylamide (DMAm, 99%), N-isopropylacrylamide (NIPAM,

97%), 2-hydroxyletthyl acrylate (HEA, 96%) were purchased from Sigma-Aldrich and N,N’-

diethylacrylamide (DEAm, 98%) was supplied by TCI chemicals. The monomers were deinhibited by

percolation through basic alumina (Ajax Chemical, AR) column. Solvents used; dimethylsulfoxide (DMSO,

99%), Tetrahydrofuran (THF, 99%), N,N’ -dimethylacetamide (DMAc, 99 %), were all supplied by Ajax

Chemical and used as received. 5,10,15,20-Tetraphenyl-21H,23H-porphine zinc (ZnTPP, 97 %) and 9,10-

dimethylanthracene (DMA, 99%) were obtained from Sigma-Aldrich and used as received. 2-

(((dodecylthio)carbonylthio)thio)propanoic acid (DTPA, 97%) was obtained from Boron Molecular and

used as received.

Instrumentation

Gel Permeation Chromatography (GPC) was used to characterize synthesized polymer with

dimethylacetamide (DMAc) and tetrahydrofuran (THF) as the eluent. The GPC instrument consists of

Shimadzu modular system with an autoinjector, a Phenomenex 5.0 µM bead sizeguard column (50 x 7.5

mm) followed by four Phenomenex 5.0 µM bead size columns (105 , 104 , 103 and 102 Å) for DMAc

system, two MIX C columns provided by Polymer Lab for THF system. Both DMAc and THF GPC systems

were calibrated based on narrow molecular weight distribution of polystyrene standards with molecular

weights of 200 to 106 g mol-1. Nuclear Magnetic Resonance (NMR) spectroscopy was carried out with

Bruker Avance III with SampleXpress operating at 300 MHz for 1H using CDCl3 as solvent.

Tetramethylsilane (TMS) was used as a reference. The data obtained was reported as chemical shift (δ)

measured in ppm downfield from TMS. UV−vis spectroscopy spectra were recorded using a CARY 300

spectrophotometer (Varian) equipped with a temperature controller. On-line Fourier Transform Near-

Infrared (FTNIR) spectroscopy was used for determination of monomer conversion by mapping the

decrement of the vinylic C-H stretching overtone of the monomer at ~ 6200 cm-1. A Bruker IFS 66/S Fourier

transform spectrometer equipped with a tungsten halogen lamp, a CaF2 beam splitter and liquid nitrogen

cooled InSb detector was used. Polymerisations under yellow (560 nm) LED light were carried out using a

FTNIR quartz cuvette (1 cm × 1 cm). Each spectrum composed of 16 scans with a resolution of 4 cm-1 was

collected in the spectral region between 7000-4000 cm-1 by manually placing the sample into the holder at

different time intervals. The total collection time per spectrum was about 10 seconds and analysis was

carried out with OPUS software. UV-vis Spectroscopy spectra were recorded using a CARY 300

spectrophotometer (Varian) equipped with a temperature controller. An Oriel VeraSol LED solar simulator

consisting of the LSS-7120 LED controller and LSH-7520 LED head was used as the light source for all

non-flow polymerisation and all other procedures. On-line Fourier Transform Infrared (FTIR) spectroscopy

was used for determination of dimethyl sulfone by measurement of the unsymmetrical S=O stretching peak

at ~1140 cm-1. A Bruker Alpha FT-IR equipped with room temperature DTGS detectors was used for

measurement. Each spectrum composed of 32 scans with a resolution of 4 cm-1 was collected in the spectral

region between 4000-500 cm-1 by dropping 2 drops of solution onto the crystal plate. Analysis was

performed using OPUS software.

Flow reactor

The flow reactor utilised 5050 SMD LEDs at 60 LEDs/m, set to green (515-525 nm) drawing a maximum

power of 14.4 W/m, at 12-24 V. The LED coil length inside the tubular reactor was 10 m. A New Era NE-

1000 multi-phaser syringe pump was used in conjunction with a Norm-Ject 20.05 mm inside diameter

syringe to inject solutions into a 1/16 inch inside diameter PTFE tubing purchased from John Morris

Scientific. The total tubing volume was calculated to be 8.7 mL and the flow rate was set to 0.145 mL/min

for 1 hour residence time. The intensity of green light at the surface of the PTFE tubing was measured to be

approximately 0.45 W/m2 using a Newport 843-R power meter.

Figure S1. Side (left) and front (right) schematic of the tubular reactor.

Figure S2. Flow reactor used for polymer synthesis. Clockwise from top left: inner PVC pipe with PTFE

tubing, outer PVC pipe with LEDs, complete reactor setup, front view of outer PVC tubing with LEDs.

General Procedure for the Synthesis of Poly N,N-Diethylacrylamide (PDEAm) via PET-RAFT

Polymerisation in the absence or presence of air and subsequent chain extension

Polymerisation of DEAm was carried out in a 1 cm × 1 cm quartz cuvette with DMSO (1000 µL, 13.98

mmol), DEAm (0.924 g, 7.27 mmol), DTPA (12.7 mg, 36.22 µmol), and ZnTPP (0.246 mg, 0.363 µmol). If

degassing was required, the vial was sealed with a rubber septum and parafilm then wrapped in aluminium

foil and degassed under nitrogen for 20 minutes. For polymerisation in the presence of air this step was

skipped. Reaction mixtures were then irradiated under LED light at room temperature (measured to be 23

˚C). After irradiation, the reaction mixture was removed from the light source in order to be analyzed by 1H

NMR (CDCl3) and GPC (DMAc) to determine the conversions, number-average molecular weights (Mn)

and dispersities (Mw/Mn). For kinetic experiments FTNIR spectroscopy was used rather than 1H NMR (see

SI, Instrumentation). For the chain extension experiments, the first block was synthesised as previously

described and conversion measured by online FTNIR spectroscopy. The successive blocks were synthesised

by addition of a 1 mL 50/50 (v/v) mixture of DMSO/DEAm to 1 mL of the previously formed polymer, and

subsequent irradiation under yellow (560 nm) 97 W/m2 light. The total irradiation time for each block in the

chain extension experiments under fully open batch conditions was 40 minutes. Molecular weight and

molecular weight distributions were measured by GPC with DMAc as eluent.

General procedure for observation of singlet oxygen in solution

The reaction protocol used in our experiments for the observance of singlet oxygen was almost identical to

that outlined by Gou and coworkers for the determination of dissolved oxygen in acrylate monomers.1 A

brief procedure is outlined here, but for more information regarding reaction components and conditions, the

interested reader is directed there. A 1 mL reaction mixture consisting of 0.1 mM ZnTPP as singlet oxygen

generator (SG) and 2mM DMA as singlet oxygen trapper (ST) in DMSO as solvent was charged to a 1 mL,

2 mm path length quartz cuvette and sealed with a cap and parafilm to ensure no gaseous headspace in the

vial. The concentrations of SG and ST as well as the dimensions of the quartz cuvette were chosen based on

the solubility of these compounds in DMSO, as well as their extinction coefficients in order to be within the

detection limits of UV-vis spectroscopy. The absorbance of the reaction mixtures before and after irradiation

with 560 nm, 15 W/m2 light was recorded at a standard time interval of 15 s. The measurements were

stopped when no further decrease of the absorption peak for DMA at 380 nm was observed. The UV-vis

spectra were baseline corrected before analysis of DMA concentrations was performed using the Beer-

Lambert law. Further experiments were conducted at varying DMSO/DEA ratios of 90/10 (v/v), 75/25(v/v),

50/50 (v/v), 25/75 (v/v), 10/90 (v/v) and 0/100 (v/v).

Table S1. Intensity and concentration variation polymerisation results

Entry Intensity (W/m2)

[ZnTPP]/[M] (ppm)

Time (min)

Conv. (%) Mn,theoa

(g/mol) Mn,gpc

b

(g/mol) Đ

1 17 50 120 82.1 20 880 16 060 1.07 2 43 50 60 84.9 21 600 17 030 1.06 3 61 50 45 82.6 21 010 16 720 1.05 4 90 50 35 82.9 21 090 16 730 1.06 5 97 50 30 80.7 20 530 16 350 1.07 6 97 10 34 77.5 19 710 15 960 1.05 7 97 5 55 81.9 20 830 15 620 1.08 8 97 1 135 79.9 20 320 17 540 1.11 Conditions: 2 mL of 50/50 (v/v) monomer/DMSO with [DEAm]:[DTPA]:[ZnTPP] = 200:1:0.01 was

irradiated under 560 nm light at ambient temperature, where the reaction vessel was fully open to the

atmosphere; a Theoretical molecular weight was calculated from the following formula: Mn,theo =

[M]0/[RAFT] × MWM × α + MWRAFT, where [M]0, [RAFT], MWM, MWRAFT and α correspond to initial

monomer concentration, initial RAFT concentration, molar mass of monomer, RAFT agent molar mass and

conversion determined by FTNIR respectively; b GPC performed in DMAc with PMMA standards, Đ

dispersity (Mw/Mn).

Table S2. Catalyst and RAFT free control experimentation in the presence and absence of oxygen

Entry Degasseda [ZnTPP] (mM)

[DTPA] (mM)

Time (min) Conv. (%)b

1 Yes 0 18.1 240 5 2 No 0 18.1 240 8 3 Yes 0.181 0 30 12c

4 No 0.181 0 30 25c

5 No 0 0 30 0c

Conditions: 2 mL of 50/50 (v/v) DEAm/DMSO with [DEAm]:[DTPA]:[ZnTPP] = 200:1:0.01 was irradiated

under 560 nm, 97 W/m2 light at ambient temperature. a Non degassed systems were fully open. b Conversion

measured by FTNIR spectroscopy; c Conversion measured by 1H NMR.

Figure S3: UV-vis spectra for DEAm solvated ZnTPP and DMA systems after 10 minutes irradiation. a)

Complete system in the absence of light irradiation; b) Degassed system containing both DMA and ZnTPP;

c) System in the absence of ZnTPP; d) System in the absence of DMA.

Figure S4: UV-vis spectra for DMSO solvated ZnTPP and DMA systems after 10 minutes irradiation. a)

Complete system in the absence of light irradiation; b) Degassed system containing both DMA and ZnTPP;

c) System in the absence of ZnTPP; d) System in the absence of DMA.

Figure S5: DMA concentration at different irradiation times in mixed DMSO/DEAm solutions. a) 90/10

(v/v) DMSO/DEAm; b) 75/25 (v/v) DMSO/DEAm; c) 25/75 (v/v) DMSO/DEAm; 10/90 (v/v)

DMSO/DEAm. Total volume = 1 mL; [ZnTPP]0 = 0.1 mmol/L; [DMA]0 = ~2 mmol/L; excitation

wavelength 560 nm, intensity 15 W/m2.

Figure S6. Proposed mechanism for PET-RAFT polymerisation in the presence of oxygen. 3Σ = ground state

oxygen, 1∆ = singlet oxygen, TTA = triplet-triplet annihilation, PET = photoinduced energy transfer, DMSO

= dimethyl sulfoxide, DMSO2 = dimethyl sulfone.

Figure S7. Comparison of molecular weight distributions recorded using a RI and UV (λ = 305 nm)

detector. Conversion was determined to be 90 % from 1H NMR in CDCl3.

Figure S8. 1H NMR spectrum of DMSO solvated ZnTPP solution after 18 h irradiation under 97 W/m2 560

nm light.

Figure S9. 1H NMR spectrum of reaction mixture after fully open polymerisation of DEAm

Figure S10. 1H NMR spectra showing increase in DMSO2 (δ 2.95 ppm) relative to DMSO (δ 2.58 ppm).

Blue (bottom): 0 minutes; Red (2nd from bottom): 1 minute; Green (middle): 3 minutes; Purple (2nd from

top): 5 minutes; Yellow (top): 10 minutes.

Rate equation derivation for initiation of RAFT agent

Where PC = ZnTPP.

The rate of RAFT agent activation is given by:

rA = kA [3ZnTPP] [RAFT]

Where kA is the rate constant for electron/energy transfer from 3ZnTPP* to RAFT. Similarly, the rate of

deactivation of 3ZnTPP is given by:

rD = kD [3ZnTPP] C

Where C is a constant, and kD is the rate constant for all other deactivation pathways of 3ZnTPP. In our

system deactivation can occur through intersystem crossing of 3ZnTPP to 1ZnTPP (radiative) or through

non-radiative relaxation through interaction with solvent, monomer, oxygen or impurities within the reaction

mixture. Also,

[3ZnTPP] = øT [ZnTPP]

Where øT is the quantum yield of triplet state formation of ZnTPP.

Now, the quantum yield of initiation, øi, is given by:

øi = rA/ (rA + rD) = ���

������� �

���������� �����

���� =

��� �

��� ����

Where β = kD/kA. Now, the rate of initiation of RAFT agent, ri, is given by:

ri = øi Iabs

Where Iabs is the intensity of absorbed light

Iabs is related to the incident light intensity by the Beer-Lambert law

Iabs = I0 × 10-ε c l

Where ε is the molar attenuation coefficient of ZnTPP at the irradiation wavelength, c is the concentration of

ZnTPP in the solution and l is the average path length of the incident light.

Additional References:

(1) Gou, L.; Coretsopoulos, C. N.; Scranton, A. B. Journal of Polymer Science Part A: Polymer

Chemistry 2004, 42, 1285.