Reversible addition-fragmentation chain transfer polymerization of alkyl-2-cyanoacrylates: An assessment of livingness

Abstract

Alkyl 2‐cyanoacrylates (CAs) are primarily used as instant adhesives, including those sold under the Loctite brand. The adhesive action can be inhibited with acid stabilizers allowing radical polymerization to be employed. The following article details the first attempted controlled/living radical polymerization of alkyl CAs: Reversible addition fragmentation chain transfer (RAFT) polymerization mediated by a poly(methyl methacrylate) dithiobenzoate macroRAFT agent for three different CA monomers (ethyl 2‐cyanoacrylate, n‐butyl 2‐cyanoacrylate, and 2‐phenylethyl cyanoacrylate) allowed the preparation of the first block copolymers of this challenging but commercially important monomer class. Nevertheless, GPC with UV detection indicated significant loss of the RAFT end‐group for all three CAs limiting control/living character. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1397–1408

Radical Polymerization of Alkyl 2-Cyanoacrylates

“…These act by proton transfer to terminate anionic or zwitterionic species, before significant chain growth occurs. Anionic inhibitors have included Lewis acids, such as BF 3 complexes [48], as well as, acetic acid [50,51,52,53], dichloroacetic acid [54], trifluoroacetic acid [55], methanesulfonic acid [47], and 1,3-propanesultone [51,56,57,58]. Excessive acidity should, however, be avoided, due to the potential for the hydrolysis of the monomer/polymer ester functionality leading to interference with the polymerization (see above).…”

“…In order to study the radical polymerization of CAs, inhibitors should be removed by distillation prior to commencing the reaction [58]. Any glassware that will come in contact with CAs should be acid washed, acetone rinsed, and oven dried before use.…”

“…For solution polymerizations, attention should be paid to the inhibitor contained within commercial solvents which can often be nucleophilic in nature [46]. Similarly, any non-solvents used to isolate poly(CAs) by precipitation should be inhibited with strong acid (e.g., MeSO 3 H) to prevent anionic polymerization of residual monomers [58]. …”

“…There has been only one report on controlled/living radical polymerization of CAs, which used reversible addition-fragmentation chain transfer (RAFT) [58]. RAFT is perhaps the most versatile reversible deactivation (controlled/living) radical polymerization technique for making precision polymers [101].…”

Controlled living anionic polymerization of cyanoacrylates by frustrated Lewis pair based initiators

“…Random cyanoacrylate copolymerization with vinyl monomers has been reported by radical,24,25 and metal catalysed initiators 26. Recent studies showed that the use of RAFT agents did not promote ideal living block polymerization of CA 27…”