Atom Transfer Radical Polymerization with Different Halides (F, Cl, Br, and I): Is the Process “Living” in the Presence of Fluorinated Initiators?

Abstract

Atom transfer radical polymerization (ATRP) is often used for grafting from fluorinated polymers. Nevertheless, the possibility to initiate an ATRP from a C–F functionality and the activity of the catalysts in the presence of fluoride anions are essentially unexplored. Therefore, we investigated the thermodynamics and kinetics of C–F bond activation by ATRP catalysts and compared it with other halide systems. The ATRP equilibrium constant was estimated to be small for the reaction between [CuITPMA]+ and benzyl fluoride (TPMA = tris­(2-pyridyl­methyl)­amine). However, [CuITPMA]+ could react with the more active initiator diethyl fluoromalonate (DEFM). With DEFM as initiator and CuIBr/TPMA as catalyst, ATRP of methyl acrylate and styrene displayed initiation efficiencies of 73% and 95%, respectively. ATRP deactivation by [F–CuIITPMA]+ was slow and followed by even slower activation of newly formed C–F bonds, leading to limited conversion. Comparison with other halides indicates that Br- and Cl-based ATRP systems are more efficient that I- and F-based systems.

Mechanism of supplemental activator and reducing agent atom transfer radical polymerization mediated by inorganic sulfites: experimental measurements and kinetic simulations

“…The $K_{\text{Br}}^{\text{II}}/K_{\text{Br}}^{\mathrm{normalI}}$ in different MA/EtOH/H 2 O mixtures was calculated from eqn (1). $K_{\text{Br}}^{\text{II}}/K_{\text{Br}}^{\mathrm{normalI}}$ predominately depends on $K_{\text{Br}}^{\text{II}}$, 41,81 therefore its sharp decrease confirmed that the value of $K_{\text{Br}}^{\text{II}}$ was strongly decreased by adding water.…”

“…The activity of an ATRP catalyst also depends on its halidophilicity ( $K_{\mathrm{normalX}}^{\text{II}}$), 80,81 i.e. the catalyst’s ability of capturing the halide anion.…”

Why Do We Need More Active ATRP Catalysts?

“…Alkyl bromides are the most commonly used ATRP initiators. The value of K ATRP for the reaction between Cu/TPMA and benzyl halides (BnX) reached the maximum for X=Br (Figure ) . Indeed, the C−X bond becomes stronger in the order X=I<Br<Cl<F, thus rendering the halogen abstraction more difficult.…”

“… Bond dissociation energy (BDE) of benzyl halides Bn−X bond, relative halidophilicities of Cu II /L and Cu I /L, and K ATRP,X / K ATRP,Br ratio for the reaction of Cu I /TPMA and BnX (X=F, Cl, Br, I). Reprinted with permission from ref . Copyright 2017, American Chemical Society.…”

Poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) Modification via Organocatalyzed Atom Transfer Radical Polymerization

“…In Figure S2 in Supporting Information, little difference was observed between original P(VDF‐ co ‐CTFE) and copolymer. It was assumed that C–F bonds were in intact under the conditions of photoinduced O‐ATRP . Slightly reduced intensity of peak i (C F Cl) was attributed to MMA insertion into C–Cl bond.…”