Aqueous SET-LRP catalyzed with “in situ” generated Cu(0) demonstrates surface mediated activation and bimolecular termination

Abstract

The aqueous SET-LRP catalyzed with "in situ" generated Cu(0) of the two amphiphilic monomers 2-hydroxyethyl acrylate (HEA) and oligo(ethylene oxide) methyl ether acrylate (OEOMEA) was investigated at temperatures from −22 to +25°C. while the theoretical value would have to be ∼0%. This high experimental chain-end functionality was explained by the slow desorption of the hydrophobic backbone containing the propagating radicals of these amphiphilic polymers from the surface of the catalyst due to their strong hydrophobic effect.Polymer radicals adsorbed on the surface of Cu(0) undergo monomer addition and reversible deactivation but do not undergo the bimolecular termination that requires desorption. This amplified adsorptiondesorption process that mediates both the activation and the bimolecular termination explains the unexpectedly high chain-end functionality of the polymers synthesized by SET-LRP.

Cu(0)-Mediated Living Radical Polymerization: A Versatile Tool for Materials Synthesis

“…The temperature is maintained at 0°C for the duration of the polymerization. 83 and oligo(ethylene oxide) methyl ether acrylate (OEOMEA) 38,84,85 have also been reported to be compatible with SET-LRP. Careful optimization of the solvent system (see section 3.2) allows access to the SET-LRP of long alkyl monomers, including lauryl acrylate (LA), 86 octadecyl acrylate (OA), 86 and semifluorinated acrylates 87,88 (e.g., 1H,1H,2H,2H-perfluorooctyl acrylate (PFOA), 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA), 1H,1H,5H-octafluoropentyl acrylate (OFPA), 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA)).…”

“…187 In addition, relatively small changes in ligand concentration can dramatically affect the end-group fidelity of the polymer chains, highlighting the importance of the ligand in Cu(0)-mediated polymerizations. 84 netriamine (PMDETA), 58,71,79,92,96,134,135,138,150 and tris(2-aminoethyl)amine (Tren) 79,136 have also been utilized as disproportionation in the presence of these ligands is near quantitative and polymerization proceeds with equally high end-group fidelity although a bit slower. 189 Interestingly, although Tren provided a slower polymerization rate when compared with Me 6 -Tren, the high end-group functionality was maintained demonstrating that the commercially available Tren is also an efficient ligand.…”

A multiple-stage activation of the catalytically inhomogeneous Cu(0) wire used in SET-LRP

“…4). 10 Only some minor changes of the Cu(0) wire due to nucleation by its large surface were detected during SET- CH 3 COOH washing demonstrates that acetic acid, previously used as solvent during SET-LRP, activates the Cu(0) wire in situ 40 just as methacrylic acid 42 and fluorinated alcohols do.…”

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The surface of Cu(0) wire used as catalyst in the single electron-transfer living radical polymerization (SET-LRP) is inhomogeneous since it contains predominantly a combination of Cu(111) and Cu (100) faces of the face centered cubic unit cell of the copper single crystal. An increase of Cu(0) wire activity up to 82% was accomplished via this new and simple activation method.Single electron transfer -living radical polymerization (SET-LRP) is most frequently catalyzed with Cu(0) powder of various particle sizes, 1-3 Cu(0) wire, 4-7 Cu(0) nanopowder generated externally by disproportionation of Cu(I)X and then isolated, 5,8 Cu(0) produced by disproportionation of Cu(I)X in situ, 9,10,11 and also Cu(0) obtained by the reduction of Cu(II)X 2 with NaBH 4 in situ. The activity of these faces towards SET reactions is substrate dependent, and therefore, aside from the Cu 2 O available on the surface, the ratio between the areas of these two crystal faces determines the catalytic activity of the wire.

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The effect of ligand, solvent and Cu(0) source on the efficient polymerization of polyether acrylates and methacrylates in aqueous and organic media

“…electric current, 14 photo irradiation [15][16][17] or chemical additives (e.g. [37][38][39][40] More sophisticated macrostructures, such as multiblock copolymers could also be synthesized upon careful optimization of the catalytic system, with high tolerance over the backbone functionalities. Among them, the use of a reducing agent/supplementary activator offers a simple route .…”