Selecting the Optimal Reaction Conditions for Copper-Mediated Atom Transfer Radical Polymerization at Low Catalyst Concentration

Atom transfer radical polymerization of an epoxide‐containing monomer, 4‐vinylphenyloxirane, employing low concentration of catalyst: synthesis of linear and star‐shaped macromolecules

“…The nature of alkyl bromide initiator (Et 2 MBrM or EBiB) did not affect noticeably the degree of polymerization control. Et 2 BrMM is known to be a more efficient ATRP initiator than EBiB and is much more useful in the low‐catalyst‐concentration ATRP of methacrylates, but, as expected, EBiB proves to be an efficient initiator in the ICAR ATRP of styrenes (in this case, 4VPO), as indicated by comparison of the polymerization data from polymerizations initiated by the two alkyl halides. It was noticed (Fig.…”

“…The relatively broad molecular weight distributions could be attributed to side reactions, some of which are related to the opening of the epoxide group by nucleophiles present in the reaction system. Recently, it was shown that the ATRP of GMA carried out under ICAR ATRP conditions yielded well‐defined polymers with narrow molecular weight distributions, provided that an efficient initiator was used and that the monomer was carefully purified prior to use. ARGET ATRP was shown to be unsuitable for the synthesis of well‐defined polyGMA because the reducing agents needed to regenerate the ATRP activator, or the products of their oxidation, could react with the epoxide groups from the monomer and/or the produced polymer.…”

“…In cases where reactive functional monomers (including epoxide‐based ones) are being polymerized, side reactions may occur during the polymerization between the monomer or polymer functionalities and the reducing agent or its oxidation product. Further, nucleophilic or basic reducing agents can react with the alkyl halide‐type chain ends and effectively ‘kill’ the living chains . All mentioned reactions affect negatively the polymerization control.…”

Epoxides as Reducing Agents for Low‐Catalyst‐Concentration Atom Transfer Radical Polymerization

“…The polymerizations of GMA were conducted with Et 2 BrMM as the initiator, which was selected because of its higher efficiency in the low‐catalyst‐concentration ATRP of methacrylates compared to the more “traditional” ethyl 2‐bromoisobutyrate . “Classical” ARGET ATRP is unsuitable for the synthesis of well‐defined polyGMA because the reducing agents needed to regenerate the ATRP activator, or the products of their oxidation, are usually rather reactive towards epoxides .…”

“…For instance, the reducing agent and the products of its oxidation present in ARGET ATRP systems need to be removed at the end of the reaction to attain pure polymer. In certain cases, these substances may also be able to participate in side reactions with functional monomers and polymers or with polymer chain ends, which leads to worsening or even loss of polymerization control. Controlled polymerization can also be conducted in systems employing Cu 0 as a reducing agent and supplementary activator of alkyl halides; the method has been demonstrated to be very efficient for the synthesis of well‐defined materials such as multisegmented copolymers .…”