Ultrasound Promoted Step‐Growth Polymerization and Polymer Crosslinking Via Copper Catalyzed Azide–Alkyne “Click” Reaction

Abstract

Mechano-activated chemistry is a powerful tool for remodeling of synthetic polymeric materials, however, few reactions are currently available. Here we show that using piezochemical reduction of a Cu -based pre-catalyst, a step-growth polymerization occurs via the copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction to form a linear polytriazole. Furthermore, we show that a linear polymer can be crosslinked mechanochemically using the same chemistry to form a solid organogel. We envision that this chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials.

Mechanically Initiated Bulk‐Scale Free‐Radical Polymerization

“…Inspired by this, we and others have successfully demonstrated the mechanically controlled atom‐transfer radical polymerization by piezochemical reduction of Cu II complexes wherein mechanical energy is transformed into chemical energy for synthesizing new materials . More recently, we expanded the scope of this methodology to step‐growth polymerization and polymer crosslinking by Cu I ‐catalyzed click reactions . However, there has not yet been a piezochemical reaction capable of bulk‐scale radical‐chain growth analogous to azobis(isobutyronitrile) (AIBN).…”

Mechanically Initiated Bulk‐Scale Free‐Radical Polymerization

“…Crosslinking polymerization mediated by mechanical force provided us with the capability to fabricate polymers with aw ider range of materials properties. [4] Thus,w e investigated the application of mechanoradical crosslinking polymerization to construct polymeric gels.A sm entioned before,t he use of HEMA as am onomer generated ap oly-(HEMA) gel without the need for ac rosslinker.S ubsequently,w et ested whether mechanoradicals could generate ar adical gel using poly(MA) with ethylene glycol dimethylacrylate (EDGMA) as the crosslinker.During the mechanoradical crosslinking reaction, the solution transitioned into as olid gel (see Figure S9). Mechanically initiated poly(MA) and poly(HEMA) gels both formed stable solid polymeric composites after removing excess solvent (Figure 3).…”

“…[3] More recently,weexpanded the scope of this methodology to stepgrowth polymerization and polymer crosslinking by Cu Icatalyzed click reactions. [4] However,t here has not yet been ap iezochemical reaction capable of bulk-scale radical-chain growth analogous to azobis(isobutyronitrile) (AIBN). Here we show,amechanically controlled free-radical (mechanoradical) polymerization and polymer crosslinking by apiezocatalytic reaction.…”

Electrochemically Mediated Aqueous Atom Transfer Radical Polymerization of N,N‐Dimethylacrylamide

“…[16][17][18][19][20][21][22][23][24][25] ATRP is catalyzed by transition metal complexes and many metals have been tested [26] but over the years the process has been refined to use small amounts of copper complexes with polydentate amine ligands. [27] Indeed, techniques such as initiators for continuous activator regeneration (ICAR) ATRP, [28,29] activators regenerated by electron transfer (ARGET) ATRP, [30][31][32][33] supplemental activator and reducing agent (SARA) ATRP, [34][35][36][37][38][39][40] photoATRP, [41][42][43][44] electrochemically mediated ATRP (eATRP), [45][46][47][48][49][50][51][52] mechanoATRP, [53] sono-ATRP [54][55][56][57][58] allowed well-controlled polymerizations with catalyst amounts down to parts per million levels relative to the monomer. Scheme 1 illustrates the mechanism of eATRP catalyzed by Cu complexes with multidentate nitrogen-based ligands (L).…”