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

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2012-07, Vol.50 (14), p.2957-2966
• Main Authors: Farrell, David J., McArdle, Ciaran, Doherty, Michael, Kelly, John M.
• Format: Article
• Language: English
• Subjects: adhesion; Adhesive strength; Aluminum; ambient temperature epoxy polymerization; anaerobic epoxy; Applied sciences; Bonding strength; Cationic polymerization; cationic polymerizations; Copolymerization; Copper; Curing; Exact sciences and technology; Fourier transforms; Glass substrates; Glass transition temperature; High temperature; Lewis acid; Line interfaces; Metal surfaces; Monomers; one-part epoxy; one‐part epoxy; Polyethers; Optimization; Organic polymers; Physicochemistry of polymers; Polyethers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; redox acid generation; redox cationic polymerization; redox polymers; Room temperature; Silver; surface promoted cationic; surface promoted polymerization; Tetrahydrofuran; Vinyl ethers
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.26082

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 A new approach to the surface promoted redox cationic polymerization of epoxy monomers based on the direct reduction of silver salts of non‐nucleophilic anions by metallic substrates was investigated. All surface promoted polymerizations were followed using FTIR‐attenuated total reflectance. Ag(I) surface promoted redox cationic polymerization was shown to have the general performance and storage stability of typical redox anaerobic acrylate adhesives, in addition to thermal properties particular to polyethers.