Externally controlled atom transfer radical polymerization

Abstract

Spatial and temporal regulations of ATRP by external stimuli are presented. Various ATRP techniques, eATRP, photoATRP, and mechanoATRP, are controlled by electrical current, light, and mechanical forces, respectively. Conversely, ARGET and SARA ATRP are controlled by chemical reducing agents. ICAR ATRP is a thermally regulated process through decomposition of a radical initiator. The aim of this review is to highlight the use of external regulations in ATRP and to summarize the state-of-the-art and future perspectives, focusing on mechanistic aspects, synthetic procedures, preparation of polymers with complex architectures and functional materials, and their applications.

Highly Cumulated Radical Cascade Reaction of aza‐1,6‐Enyenes: Stereoselective Synthesis of exo‐Methylene Piperidines

“…For example, tandem radical cyclization provides a convenient methodology to form multi‐cyclic structures in one step, and development of this strategy has attracted considerable attention among synthetic chemists . Organic radicals typically prefer addition or cyclization reactions; conversely, direct substitution or rearrangement reactions involving organic radicals are relatively rare, although ATRC and ATRP reactions are known in copper mediated radical reactions . Recently, we successfully demonstrated a radical cascade reaction including direct radical substitution reaction on tin atom to give bicyclic stannolanes in good yields in a stereoselective manner .…”

Biocompatible polymers via aqueous electrochemically mediated atom transfer radical polymerization

“…Indeed, radical termination in ATRP causes the accumulation of [XCu II L] + deactivators, ultimately leading to early halt of the polymerization. This could be overcome by continuously regenerating the [Cu I L] + activator through either chemical, photochemical, electrical, sonochemical, or mechanical stimuli …”

“…The unique advantage of e ATRP is the absence of by‐products in solution, since only electrons are introduced into the system to reduce [XCu II L] + . Conversely, various products are generated in solution by the reaction of conventional radical initiators, reducing agents and electron donors employed in initiators for continuous activator regeneration (ICAR), activator regenerated by electron transfer (ARGET), and photochemically mediated ATRP, respectively . Moreover, in e ATRP, the ratio between Cu(II) and Cu(I) species at the electrode is tuned by modifying the applied potential, according to the Nernst equation (), where E θ is the standard reduction potential of the redox couple [XCu II L] + /[XCu I L], R is the gas constant, T is the temperature, and F is Faraday's constant. …”

Alkylboranes in Conventional and Controlled Radical Polymerization

“…The polymerizations with various targeted degrees of polymerization ranging from 50 to 800 successfully provided the polymers with pre‐determined molecular weight and narrow molecular weight distribution (Figure (a,b)). The externally controlled CRP received lots of interests, including electrical current, light, and mechanical forces as external stimuli. This work provided oxygen gas or air gas as a new type of external regulator to give the temporal and spatial control of the RAFT polymerization (Figure (c)).…”