Francesca Lorandi

Sustainable Electrochemically-Mediated Atom Transfer Radical Polymerization with Inexpensive Non-Platinum Electrodes.

Electrochemically-mediated atom transfer radical polymerization (eATRP) of oligo(ethylene oxide) methyl ether methacrylate in water is investigated on glassy carbon, Au, Ti, Ni, NiCr and SS304. eATRPs are performed both in divided and undivided electrochemical cells operating under either potentiostatic or galvanostatic mode. The reaction is fast, reaching high conversions in ≈4 h, and yields polymers with dispersity <1.2 and molecular weights close to the theoretical values. Most importantly, eATRP in a highly simplified setup (undivided cell under galvanostatic mode) with inexpensive nonnoble metals, such as NiCr and SS304, as cathode is well-controlled. Additionally, these electrodes neither release harmful ions in solution nor react directly with the CX chain end and can be reused several times. It is demonstrated that Pt can be replaced with cheaper, and more readily available materials without negatively affecting eATRP performance.

Electrochemically mediated atom transfer radical polymerization of n-butyl acrylate on non-platinum cathodes

Traditionally, electrochemically mediated atom transfer radical polymerization (eATRP) is performed with Pt electrodes, but extensive use of such an expensive, rare, and non-functionalizable metal may pose some limitations to the method, owing mainly to the high cost of the experimental setup and the limited natural resources of platinum. As a further development of eATRP, polymerization of n-butyl acrylate in dimethylformamide was investigated employing different cathodic materials: glassy carbon, gold, iron, nickel–chromium, and stainless steel. With all these electrodes, eATRP was fast (conversion >85% in 2 h) and well-controlled (dispersity <1.2) under a wide range of experimental setups. To show the robustness of eATRP with inexpensive non-noble electrodes (i) the catalyst loading was reduced to less than 75 ppm, (ii) the same cathode was reused several times without reactivation, and (iii) undivided cells with all non-platinum electrodes were used. Lastly, all electrodes were stable and did not significantly release metal ions in solution, merely acting as an electron sink for the reduction of the catalyst.

Miniemulsion ARGET ATRP via Interfacial and Ion-Pair Catalysis: From ppm to ppb of Residual Copper

It was recently reported that copper catalysts used in atom transfer radical polymerization (ATRP) can combine with anionic surfactants used in emulsion polymerization to form ion pairs. The ion pairs predominately reside at the surface of the monomer droplets, but they can also migrate inside the droplets and induce a controlled polymerization. This concept was applied to activator regenerated by electron transfer (ARGET) ATRP, with ascorbic acid as reducing agent. ATRP of n-butyl acrylate (BA) and n-butyl methacrylate (BMA) was carried out in miniemulsion using CuII/tris(2-pyridylmethyl)amine (TPMA) as catalyst, with several anionic surfactants forming the reactive ion-pair complexes. The amount and structure of surfactant controlled both the polymerization rate and the final particle size. Well-controlled polymers were prepared with catalyst loadings as low as 50 ppm, leaving only 300 ppb of Cu in the precipitated polymer. Efficient chain extension of a poly(BMA)-Br macroinitiator confirmed high retention of chain-end functionality. This procedure was exploited to prepare polymers with complex architectures such as block copolymers, star polymers, and molecular brushes.

Ab Initio Emulsion Atom‐Transfer Radical Polymerization

Stable latexes of poly(meth)acrylates with predetermined molecular weights, narrow molecular-weight distributions, and controlled architecture were prepared by true ab initio emulsion atom-transfer radical polymerization. Water-soluble (macro)initiators in combination with a hydrophilic catalyst, Cu/tris(2-pyridylmethyl)amine, initiated the polymerization in the aqueous phase. The catalyst strongly interacted with the surfactant sodium dodecyl sulfate (SDS), thereby tuning the polymerization within nucleated hydrophobic polymer particles. Long-term stable latexes were obtained, even with SDS loading below 3 wt % relative to monomer. Block and gradient copolymers were prepared in situ. The reaction volume and solid content were successfully increased to 100 mL and 40 vol %, respectively, thus suggesting facile scale-up of this technique. The proposed setup could be integrated in existing industrial plants used for emulsion polymerization.