Nitrone‐Mediated Radical Coupling of Polymers Derived from Reverse Iodine‐Transfer Polymerization

Abstract

The current study describes the synthesis of iodine-end-capped polystyrene (PS) and poly(methyl methacrylate) (PMMA) precursors using reverse iodine-transfer polymerization, which, in a second step, are used in nitrone-mediated radical coupling (NMRC) reactions. Initially, the reverse iodine polymerization of both monomers is studied and optimized in order to obtain iodine-end-capped materials with controlled molecular weights and low dispersities. Subsequently, NMRC of both PS and PMMA precursors is carried out in the presence of CuCl as a halide-exchange agent. Coupling effi ciencies of x c = 0.754 for PS-I and 0.84 for PMMA-I are observed; however, the addition of 10 equivalents of styrene is required to promote the coupling in the case of methacrylate. The presence of the desired alkoxyamine functionality in mid-chain position of the products is evidenced via quenching experiments.

Reversible Surface Engineering via Nitrone-Mediated Radical Coupling

“…59,60 More recently, NMRC has also been used to couple polymers derived from reverse iodine-transfer polymerization, further underpinning that any precursor of nonpersistent radicals can be employed. 61 We herein exploit both key features of NMRC, i.e., dynamic covalent reversibility and postcoupling NMP, for surface grafting. We have selected two approaches on flat surfaces and further on particles for quantification.…”

“…Even though dynamic covalent exchange/reversibility and postcoupling block copolymerization are excellent features of alkoxyamines obtained from NMRC, nitrones received the most attention in synthetic organic chemistry for their use in [2 + 3] cycloadditions − and as radical spin-traps − yet only little in the context of polymer chemistry . Initially, nitrones were assessed as control agents in enhanced spin-capturing polymerization ,− and further as coupling reagent in nitrone-mediated radical coupling (NMRC) that allows for the introduction of a new midchain alkoxyamine functionality, , e.g., to construct dendrimers, star polymers, and other architectures. , More recently, NMRC has also been used to couple polymers derived from reverse iodine-transfer polymerization, further underpinning that any precursor of nonpersistent radicals can be employed …”

Reverse iodine transfer polymerization of vinyl acetate and vinyl benzoate: synthesis and characterization of homo- and copolymers

“…Controlled radical polymerization (CRP) allows the synthesis of polymers with controlled molecular weight, relatively low polydispersity index (PDI < 1.1), controlled molecular architecture and composition, and diverse functionality . Iodine transfer radical polymerization (ITP) is one of the most prominent CRP methods, in which an initiating radical based on degenerative transfer leads to entering of iodo compounds in a controlled process . However, ITP has two major limitations .…”

Visible light-induced controlled radical polymerization of methacrylates with perfluoroalkyl iodide as the initiator in conjugation with a photoredox catalyst fac -[Ir(ppy)]3

“…However, organoiodine compounds are very efficient chain transfer agents in free radical polymerization . The earliest example of applying organic‐iodide (iodoform) as chain transfer agents in free radical polymerization was carried out with AIBN as the initiator, giving polymer chains with iodine atom ends.…”