New Initiating Systems for Thermal Cationic Polymerization at Ambient Temperature with in situ Formation of Ag(0) Nanoparticles: A Silane/Silver Salt Combination

Abstract

International audienceNew initiating systems for the thermal cationic polymerization of epoxides and vinyl ether derivatives are proposed. They are based on a silane/silver salt interaction, which ensures a good to excellent polymerization at room temperature. Moreover, the polymerization is much more efficient under air. The effects of the silane, silver salt, and monomer structures are investigated. Interestingly, silver nanoparticles Ag(0) are formed in situ. A coherent picture of the involved chemical mechanisms is presented

N-Vinylcarbazole: As an Additive for Thermal Polymerization at Room Temperature with in situ Formation of Ag(0) Nanoparticules

“…They ensure good to excellent polymerizations are always obtained leading to tack free surface coatings after only 3 min. A concomitant increase of the band at 1080 cm is also observed due to the formation of the polyether network and polyacrylate, respectively (Figure 5B) [30][31][32]. A high Si-H consumption is also found in agreement with the proposed mechanisms (Schemes 1 and 2) ( Figure 5C).…”

“…A quite good polymerization is always obtained at RT and under air leading to tack free surface coatings (gel time ~5 min and tack free time ~1 h). It is evident the important decrease of the typical epoxy band at 770-830 cm due to ether group formed during the ring-opening polymerization ( Figure 4B) [30][31][32][33][34][35][36][37]. Almost no inhibition is noted, as a short period is already requested for the solubilization of the silane into the formulation.…”

“…This approach consists of producing a radical R • (from an organosilane), to initiate FRP, that can be easily oxidized by a silver salt (e.g., AgSbF6) leading to R + , which corresponds to the ROP initiating structure (Scheme 2) [30][31][32] However, the nature of the primary radicals produced from the organosilane is crucial for getting a high polymerization efficiency, as they should be characterized by excellent oxidation properties; moreover, the resulting radicals and cations must be efficient structures for the FRP and CP reactions, respectively [33][34][35][36][37]. Even if a lot of systems have been developed in the last years [33][34][35][36][37][38][39][40][41][42], the search for novel additives being able to improve the radical and/or cationic polymerization processes still appears as a challenge.…”

In situ production of visible light absorbing Ti-based nanoparticles in solution and in a photopolymerizable cationic matrix

“…The in-situ incorporation of NPs has been achieved in acrylate monomer/oligomer matrices (see e.g. ref [9][10][11][12][13][14][15] and references therein). In such media, the photoinitiation step and the NPs formation involves a photoinitiator PI (ra) or a PI/amine AH system that produces two radicals by a homolytic cleavage (rb) or an electron/proton transfer (rc): one is used to initiate the polymerization (rd), the other to reduce a metal salt (re, rf), this last reaction generating a cationic species (re, rf); Ag, Pd, Au NPs have been thus produced.…”

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

“…4 (2) Direct reduction of silver salts of nonnucleophilic anions by an organosilane species. 5 While these systems offer interesting approaches to ambient temperature polymerization of cationically polymerizable monomers there still exists a need to develop an initiation chemistry that allows preparation of storage stable single-component epoxy compositions that polymerize at ambient temperatures. 6 Such epoxy compositions would be considered the cationically initiated analogs of existing redox radical initiated acrylic systems used commercially.…”