Radical Nature of Cu-Catalyzed Controlled Radical Polymerizations (Atom Transfer Radical Polymerization)

Abstract

Copper-catalyzed atom transfer radical polymerization (ATRP) is one of the most robust and precise techniques for controlling radical polymerization. The very good control of molecular weights, polydispersities, functionalities, chain composition, and topologies unusual for radical systems combined with the application of transition metals as catalysts requires more detailed mechanistic studies and proof of the radical nature of active species. The following results are in agreement with the radical nature of ATRP: reverse ATRP, chemoselectivities similar to those for conventional radical polymerization (effect of additives and inhibitors/scavengers, reactivity ratios, transfer coefficients), regioselectivities similar to those for conventional radical polymerization (low proportion of head-to-head units and expected structure of both tail and head end groups), stereoselectivities (tacticities) similar to that in conventional radical polymerization, EPR detection of X-Mtn+1 species resulting from the persistent radical effect, and confirmation of the termination by doubling molecular weights as well as cross-linking with multifunctional initiators and inimers. In addition, it seems that, in most ATRP systems, the contribution of degenerative transfer and reversible formation of organometallic intermediates is small and a halogen atom is transferred in the concerted process rather than in a two-step process with the involvement of radical anions.

Copolymerization of n-Butyl Acrylate with Methyl Methacrylate and PMMA Macromonomers: Comparison of Reactivity Ratios in Conventional and Atom Transfer Radical Copolymerization

“…Similar observations have been made with other comonomer pairs. [20][21][22][23][24] Using NiBr 2 (PPh 3 ) 2 as catalyst, Moineau et al 31 recently reported similar reactivity ratios (r MMA ) 1.7; r nBuA ) 0.34).…”

“Green” Atom Transfer Radical Polymerization: From Process Design to Preparation of Well-Defined Environmentally Friendly Polymeric Materials

“…[68][69][70] Cu. 26,[111][112][113][114][115][116][117][118][119][120] More details are provided in review papers and monographs. 23 126 Such systems are of fundamental interest since the presence of more than one metal complex in the reaction mixture may be beneficial, and the catalysis of more than one process may be accomplished simultaneously.…”

Synthesis of poly[?-caprolacton-b-epichlorohydryin-b-?-caprolactone]- g-poly(styrene) Block-Graft Copolymers via Cationic Ring Opening and Atom Transfer Radical Polymerization Transformations.

“…Comparing to the other living/controlled radical polymerizations techniques, the ATRP has drawn widespread attention because of its many advantages and great industrialization prospects (Wang et al, 1995b). ATRP method has served a very important purpose for the preparation of new different type functional copolymers with controlled molecular weights and low polydispersities(PDI) (Matyjaszewski 1998;Chen et al, 2015 ).…”

“…The complexes of transition metals like Cu(I), Ni(II), Ru(II), Fe(II) and Os(II) have been used as catalysts in ATRP for the preparation of block copolymers (Matyjaszewski 1998;Braunecker et al, 2007). Copper (II) based catalysts are the most convenient and cheapest in terms of cost as well.…”

“…Copper (II) based catalysts are the most convenient and cheapest in terms of cost as well. Copper(I)-catalyzed ATRP is one of the most important techniques for controlling radical polymerizations ( Matyjaszewski 1998;Tsarevsky et al, 2006).…”