Reversible Deactivation Radical Polymerization of Monomers Containing Activated Aziridine Groups

Abstract

Polymers bearing activated aziridine groups are attractive precursors to α-substituted-β-amino-functionalized materials due to the enhanced reactivity of the pendant aziridine functionalities toward ring-opening by nucleophiles. Two aziridine-containing styrenic monomers, 2-(4-vinylphenyl)aziridine (VPA) and N-mesyl-2-(4-vinylphenyl)aziridine (NMVPA), were polymerized under a variety of reversible deactivation radical polymerization conditions. Low-catalyst-concentration atom transfer radical polymerization (LCC-ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization were ineffective at producing well-defined polymers from VPA due to side reactions between the aziridine functionalities and the agents controlling the polymerizations (catalysts or chain transfer agents). PolyVPA produced under nitroxide-mediated polymerization (NMP) conditions had narrow molecular weight distribution at low to moderate conversions of monomer, but branched and eventually cross-linked polymers were formed at higher conversions due to ring-opening reactions of the aziridine groups. Most of these undesirable side reactions were eliminated by attaching a methanesulfonyl (mesyl) group to the aziridine nitrogen atom, and well-defined linear homopolymers with targeted molecular weights were realized from NMVPA under RAFT and NMP conditions; however, side reactions between the aziridine groups and the catalyst in LCC-ATRP still occured and the polymerization was uncontrolled using this technique.

Nano‐Star‐Shaped Polymers for Drug Delivery Applications

“…ATRP is an example of a technique used to attain living polymerization, and it functions on the formation of radicals from dormant alkyl halides by halogen abstraction with transition metal complexes. [24,[75][76][77][78][79][80][81][82][83] This method hinges on the fact that the equilibrium in this reaction lies largely on the side of the dormant alkyl halides, meaning that the number of radicals produced is few. This translates into a lower radical concentration, and reduces the possibility of radical termination reactions to maintain the living polymerization of the arms of these star-shaped polymers, or other polymers for that matter.…”

“…ATRP is an example of a technique used to attain living polymerization, and it functions on the formation of radicals from dormant alkyl halides by halogen abstraction with transition metal complexes . This method hinges on the fact that the equilibrium in this reaction lies largely on the side of the dormant alkyl halides, meaning that the number of radicals produced is few.…”

The living anionic polymerization of activated aziridines: a systematic study of reaction conditions and kinetics

“…To date, only such activated aziridines undergo anionic polymerization, but also a few other aziridine-containing polymers have been prepared and studied as functional polymers for postmodification. [10][11][12][13][14] The AROP of aziridines allows us to prepare well-defined poly(ethylene imine) derivatives. 4,9 We have developed new monomers and initiator-systems during the last few years, expanding this still rather unexplored approach to polysulfonamides and amines.…”

Aziridines and azetidines: building blocks for polyamines by anionic and cationic ring-opening polymerization

“…After radical polymerization, the pending sulfonyl aziridines could be further modified by nucleophilic additions, which was described for other polymers with aziridine side groups. [153][154][155][156] Also, polyols have been prepared by the AROP of sulfonyl aziridines. In analogy to ethoxy ethyl glycidyl ether (EEGE), the well-known precursor in oxyanionic polymerization to obtain linear poly(glycerol), 74,157 acetal-protected N-tosyl-activated aziridines were introduced in 2016 (Fig.…”