Rapidly self-deoxygenating controlled radical polymerization in water via in situ disproportionation of Cu(i)

Rapidly self-deoxygenating Cu-RDRP in aqueous media is investigated. The disproportionation of Cu(i)/Me6Tren in water towards Cu(ii) and highly reactive Cu(0) leads to O2-free reaction environments within the first seconds of the reaction, even when the reaction takes place in the open-air. By leveraging this significantly fast O2-reducing activity of the disproportionation reaction, a range of well-defined water-soluble polymers with narrow dispersity are attained in a few minutes or less. This methodology provides the ability to prepare block copolymers via sequential monomer addition with little evidence for chain termination over the lifetime of the polymerization and allows for the synthesis of star-shaped polymers with the use of multi-functional initiators. The mechanism of self-deoxygenation is elucidated with the use of various characterization tools, and the species that participate in the rapid oxygen consumption is identified and discussed in detail.

equipped with 2 x PLgel Mixed D columns (300 x 7.5 mm) and a PLgel 5 µm guard column. The eluent used was DMF with 5 mmol NH 4 BF 4 additive to reduce column interactions. Samples were run at 1 ml/min at 50 o C. Poly(methyl methacrylate) standards (Agilent EasyVials) were used for calibration between 955,000 -550 g mol -1 . Analyte samples were filtered through a nylon membrane with 0.22 μm pore size before injection. Respectively, experimental molar mass (M n,SEC ) and dispersity (Đ) values of synthesized polymers were determined by conventional calibration and universal calibration using Agilent GPC/SEC software.

Scanning Electron Microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy
Scanning electron microscopy was performed using a ZEISS Gemini SEM -Field Emission Scanning Electron Microscope and a ZEISS Supra. Best results were obtained when using the InLens detector with ~3.5 mm working distance, 20 (Gemini) or 30 (Supra) µm aperture and 5-15 kV acceleration voltage, with respect to sample tolerance. EDX spectroscopy and elemental analysis were performed via the Gemini instrument through its SDD EDX detector.
Sample Preparation: A 3 mL total capacity glass vial placed in an ice bath was charged with 7.2 mg (1 eq.) Cu(I)Br and 1 mL DI-H 2 O and was septum-sealed. Upon fast stirring (900 rpm), Μe 6 Tren (14 μL, 1 eq.) was added in the Cu(I)Br solution and aliquots from the heterogeneous solution were dropcast on silicon wafer chips (5 mm x 7 mm) which were attached to aluminium specimen stubs. The dropcast samples were instantly being placed under N 2 blanket and left to dry.

Spectroscopy (EELS)
TEM imaging was carried out using a JEOL 2100 electron microscope. Annular dark-field STEM imaging and EELS spectrum imaging were performed in a double-corrected JEOL ARM200f microscope, equipped with a Gatan Quantum spectrometer, operated at 200 kV. A probe convergence semi-angle of 32 mrad and a spectrometer semi-collection angle of 25 mrad were used for the collection of the EELS signals. The energy resolution of the EELS measurements was 1.2 eV, as estimated from the full-width-half-maximum of the zero-loss peaks. A DualEELS mode was used at a dispersion of 0.1 eV per channel, where the core loss spectra from either Cu or O were calibrated using the zero loss peaks in the low loss spectra.
The samples for TEM were prepared by dropcasting aliquots of the disproportionation solution onto lacey carbon grids supplied by EM Resolutions and were left to dry under N 2 blanket.

X-ray photoelectron spectroscopy (XPS)
XPS measurements were performed using a Kratos Axis Ultra DLD spectrometer. The samples were illuminated using X-rays from a monochromated Al Kα source (hν = 1486.7 eV) and detected at a take-off angle of 90°. The resolution, binding energy referencing, and transmission function of the analyser were determined using a clean polycrystalline Ag foil.
XPS peak fitting was carried out using the CasaXPS software (Voigt -mixed Gaussian−Lorentzian line shapes and a Shirley background). The peaks were corrected with respect to C 1s at 284.7 eV due to the use of the charge neutraliser to avoid surface charging.