Remarkable Versatility of Silane/Iodonium Salt as Redox Free Radical, Cationic, and Photopolymerization Initiators

Abstract

The use of safe, economic, and efficient initiators in redox free radical polymerization (RFRP) at room temperature (RT) or in cationic polymerization (CP) and as photoinitiators (PI) for both free radical polymerization (FRP) and CP as well as their use for the manufacture of composites are investigated. Remarkably, initiators based on silane/iodonium salt couples are proposed here for their versatility for all the different polymerization modes which is a quite unique feature. The reactions are followed by optical pyrometric measurements, DSC (differential scanning calorimetry), RT-FTIR (real-time Fourier transformed infrared spectrometry), and CRM (confocal Raman microscopy). In RFRP, an adjustable gel time can be controlled between 1 and 15 min by adjusting the concentrations of these redox agents (or even between 2 and 30 min upon addition of stabilizer, e.g., TEMPOL); the storage stability over 5 weeks at ambient temperature and in the dark is excellent. In FRP, up to 80% of reactive function conversion is reached. In CP, the DSC peak drops down from 175 °C (in absence of silane) to 113 °C. Remarkably, carbon or glass fiber/epoxy resin composites are easily obtained through a dual approach (two steps), i.e., fast photochemical curing for the surface associated with redox or thermal curing in depth.

Review on UV-Induced Cationic Frontal Polymerization of Epoxy Monomers

“…Wang et al [ 57 ] reported a novel combination of a photoinitiator based on diaryliodonium salt and silanes that gave adjustable gel time of polymerization as well as excellent storage stability for bisepoxides. This unique formulation provided the advantage of multi-mechanism curing, which includes redox free radical, free radical and thermal/UV-induced cationic polymerization.…”

“…This unique formulation provided the advantage of multi-mechanism curing, which includes redox free radical, free radical and thermal/UV-induced cationic polymerization. They proved the positive influence of silane groups in cationic photo polymerization of epoxy, where Si-H groups where able to participate in the initiation and promotion of epoxy polymerization [ 57 ].…”

A Sprayable and Visible Light Rapid-Cured Strippable Film for Surface Radioactive Decontamination

“…The strippable films were synthesized by visible light polymerization, as illustrated in Scheme 1 . Upon exposure to visible light, CQ is converted to an excited state before forming free radicals (CQ−H•) by abstracting a hydrogen atom from EDB [ 35 ]. TBA and side chains of 1,2-addition LPB are triggered by CQ−H• free radicals.…”

Photoinitiation mechanisms and photogelation kinetics of blue light induced polymerization of acrylamide with bicomponent photoinitiators

“…Photopolymerization is a facile approach to manufacturing of polymer materials. [1][2][3] There has been a trend of replacing ultraviolet (UV) with visible and near-infrared light. [4][5][6] Longer wavelengths have greater depth of penetration into both biological and synthetic materials, making them particularly attractive for biomedical applications.…”

“…Photopolymerization is a facile approach to manufacturing of polymer materials 1–3 . There has been a trend of replacing ultraviolet (UV) with visible and near‐infrared light 4–6 .…”