Construction of excellent thermal latent system for the synthesis of networked epoxide polymers by sulfonium salts

Abstract

An efficient thermally latent initiation system using dual sulfonium salts, consisting S‐benzylsulfonium salt 1 bearing SbF6− counter anion and S,S‐dimethylsulfonium salt 2 bearing CH3 SO4− counter anion, has been developed for the cationic polymerization of epoxides. Compared to the conventional system using 1 as a thermally latent initiator, the newly developed system allowed significant improvement of stability of epoxy formulations during storage at ambient temperature without sacrificing their curability at elevated temperatures. Such a remarkable performance is attributable to the nucleophilic attack of CH3 SO4− to cationic species formed unavoidably by the reaction of 1 with epoxide. Such entrapment of cationic species into the corresponding dormant led to the inhibition of undesirable chain growth of polymers during storage of epoxy formulations. In addition, the dormant can undergo dissociation at elevated temperature to give cationic species, which can readily initiate the polymerization of epoxide. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2096–2102

Effect of oligo(spiroorthocarbonate)s on the volume shrinkage of epoxides during crosslinking by sulfonium salt‐initiated cationic polymerization of epoxides

“…Before the polymerization, there was an absorption at 917 cm −1 attributable to the epoxy moiety of BADGE. 21 In the spectrum of the polymer, this absorption disappeared. In addition, a new absorption appeared at 1745 cm −1 , which was attributed to the carbonate moiety formed by the ring-opening polymerization of the spiroorthocarbonate moieties of 1b.…”

“…Figure shows IR spectrum of the formulation before the polymerization and that of the obtained networked polymer. Before the polymerization, there was an absorption at 917 cm −1 attributable to the epoxy moiety of BADGE . In the spectrum of the polymer, this absorption disappeared.…”

“…Here, we report a sulfonium salt‐initiated cationic copolymerization of bisphenol A‐diglycidyl ether (BADGE) and 1 (Scheme ). As the initiator, a benzylsulfonium salt BHPMS‐HFA was employed . This sulfonium salt that can be obtained easily by S ‐methylation of inexpensive 4‐(methylthio)phenol has been practically used as a thermally latent cationic initiators for polymerization of epoxides.…”

“…As the initiator, a benzylsulfonium salt BHPMS-HFA was employed. 21 This sulfonium salt that can be obtained easily by Smethylation of inexpensive 4-(methylthio)phenol has been practically used as a thermally latent cationic initiators for polymerization of epoxides. The shrinkage suppression effects of 1 and the thermal properties of the resulting polymers are presented.…”

Regulating Cationic Polymerization of Difunctional Epoxy Resin through Structural Variations of the Thermal Initiator

“…The polymerization of difunctional monomer leads to the cross-linked structure which limits the use of conventional characterization methodologies. However, this process can be examined directly and effectively using DSC measurements, − resulting in three important parameters (Figure S9). First, the onset temperature of the exothermic peak, known as the kick-off temperature ( T kick‑off ), provides the initiation temperature.…”