SET-LRP of the Hydrophobic Biobased Menthyl Acrylate

Cu(0) wire-catalyzed single electron transfer-living radical polymerization (SET-LRP) of (-)-menthyl acrylate, a biobased hydrophobic monomer, was investigated at 25 °C in ethanol, isopropanol, ethyl lactate, 2,2,2-trifluoroethanol (TFE), and 2,2,3,3-tetrafluoropropanol (TFP). All solvents are known to promote, in the presence of N ligands, the mechanistically required self-regulated disproportionation of Cu(I)Br into Cu(0) and Cu(II)Br₂. Both fluorinated alcohols brought out their characteristics of universal SET-LRP solvents and showed the proper polarity balance to mediate an efficient polymerization of this bulky and hydrophobic monomer. Together with the secondary alkyl halide initiator, methyl 2-bromopropionate (MBP), and the tris(2-dimethylaminoethyl)amine (Me₆-TREN) ligand, TFE and TPF mediated an efficient SET-LRP of MnA at room temperature that proceeds through a self-generated biphasic system. The results presented here demonstrate that Cu(0) wire-catalyzed SET-LRP can be used to target polyMnA with different block lengths and narrow molecular weight distribution at room temperature. Indeed, the use of a combination of techniques that include GPC, ¹H NMR, MALDI-TOF MS performed before and after thioetherification of bromine terminus via "thio-bromo" click chemistry, and in situ reinitiation copolymerization experiments supports the near perfect chain end functionality of the synthesized biobased hydrophobic polymers. These results expand the possibilities of SET-LRP into the area of renewable resources where hydrophobic compounds are widespread.