Surface promoted redox cationic polymerization of epoxy monomers catalyzed by silver salts

Abstract

The first example of a one‐component room temperature curing redox cationic polymerization for metal surfaces is described. A weak Lewis acid (Ag+) is used as a latent catalyst to likely generate a much stronger one (Fe2+/Fe3+ or Cu2+) at the bond line interface. Such a process has been demonstrated for 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane carboxylate using [Ag(1,5‐cyclooctadiene)2]SbF6 with the polymerization monitored most conveniently by fourier transform infrared spectroscopy (FTIR). This system, however, demonstrates a relatively low adhesive strength even following curing for 24 h. Higher bond strengths were achieved using mixtures with other cationically polymerizable monomers (vinyl ethers, tetrahydrofuran (THF), oxetanes). Factors considered for optimization of the rates and extent of reaction were the concentrations of a vinyl ether comonomer and [AgLn]X, the nature of the counterion (X), and of the ligand (L). The performance of the Ag(I) system was compared to that of Cu(I) and various organic cations and the activity of the redox cationic polymerizations on a range of metallic (iron, copper, and aluminium) and nonmetallic (glass and various plastics) substrates was studied. A relatively high glass transition temperature was recorded for the optimized model system and the bonding strength at elevated temperature (150–200 °C) following a room temperature cure was found to be attractive compared to selected model anaerobic acrylate compositions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Redox two-component initiated free radical and cationic polymerizations: Concepts, reactions and applications

“…Graft polymerization of surfaces was also proposed via redox cationic (silver salt/Fe(0) surface) polymerization of activated epoxides (EPOX). The adhesive properties were competitive with two anaerobic (Loctite®) acrylate products [192] showing the importance of developing RCP methods in the adhesive industry.…”

“…Next, dialkyl borane 9-BBN does not require any noble metal catalysts and proceeds via a direct and efficient reduction of the iodo nium salt (entry 5). In a more exotic way, ferrocenium (III) was proposed as initiating the RCP of EPOX from a surface but the reaction was found quite slow (several hours) [192]. Another option is to use Ag(I)/Silane reaction to produce cations.…”

“…adhesives [199]), multifunctional monomers are used for example (3,4-epoxycyclohexane) methyl 3,4-epoxycyclohexylcarboxylate (or EPOX) activated epoxide. They also result in polymers with high glass transition temperatures (T g > 130°C) [192]; nevertheless, they are still relatively expensive compared to FRP monomers. The adhesive properties of epoxides to many substrates, the low shrinkage and the absence of oxygen inhibition encourage the development of novel multifunctional monomers compatible with CP [183,200].…”

“…This lead to on-demand dual cationic/radical polymerizations that were applied to vinylether/ acrylate copolymerization. Ferrocene and ferrocenium chemistry is also largely present in conventional redox polymerizations [64,67,69,192,240]. In both modes (controlled or conventional), ferrocene-based redox agents enable outstanding accelerating effects and reactions under mild conditions.…”