Temporally Controlled Ultrasonication‐Mediated Atom Transfer Radical Polymerization in Miniemulsion

Abstract

Due to the increasing requirement for more environmentally and industrially relevant approaches in macromolecules synthesis, ultrasonication‐mediated atom transfer radical polymerization (sono‐ATRP) in miniemulsion media is applied for the first time to obtain precisely defined poly(n‐butyl acrylate) (PBA) and poly(methyl methacrylate) (PMMA) homopolymers, and poly(n‐butyl acrylate)‐block‐poly(tert‐butyl acrylate) (PBA‐b‐PtBA) and poly(n‐butyl acrylate)‐block‐poly(butyl acrylate) (PBA‐b‐PBA) copolymers. It is demonstrated in the reaction setup with strongly hydrophilic catalyst copper(II) bromide/tris(2‐pyridylmethyl)amine (CuIIBr2/TPMA) responsible for two principal mechanisms – interfacial and ion‐pair catalysis reflecting single‐catalyst approach. This solution turns out to be an excellent tool in controlled preparation of well‐defined polymers with narrow molecular weight distribution (up to Ð = 1.28) and preserves chain‐end functionality (DCF = 0.02% to 0.32%). Temporal control over the polymer chain growth is successfully conducted by turning the ultrasonication on/off. Taking into consideration long OFF stage (92.5 h) during ultrasonication‐induced polymerization in miniemulsion, synthesis is efficiently reinitiated without any influence on controlled characteristics maintaining the precise structure of received PBA homopolymers, confirmed by narrow molecular weight distribution (Ð = 1.26) and high retention of chain‐end functionality (DCF = 0.01%). This procedure constitutes an excellent simple and eco‐friendly approach in preparation of functional polymeric materials.

Synthesis of Riboflavin‐Based Macromolecules through Low ppm ATRP in Aqueous Media

“…Analysis of RF-(PBA-Br) 2 Polymer Chains: The analysis of the chains length of polymer brushes was conducted by cleaving the PBA chains attached to the riboflavin core by acid solvolysis according to the procedure described in reference. [33] The resulting polymers were analyzed by DMF GPC, determining apparent M n and Ð of PBA chains. 2 Macromolecules via ARGET ATRP: TEABr (0.74 g, 3.5 mmol) and NIPAM (3.22 g, 28.5 mmol) were placed in a seven neck cell maintained at 0 °C under a slow N 2 purge.…”

“…It can be triggered by the introduction of a reducing compound, for example, radical initiator in initiators for continuous activator regeneration (ICAR) ATRP, [20] chemical reducing agents (e.g., glucose, [21] ascorbic acid, [22] hydrazine [21] ), and metallic silver [23,24] in activators regenerated by electron transfer (ARGET) ATRP, zerovalent metals (Fe 0 , Cu 0 ) [24][25][26] in supplemental activator and reducing agent (SARA) ATRP. Alternatively, an external stimuli such as a reducing current in electrochemically mediated ATRP (eATRP) [27][28][29][30] and simplified electrochemically mediated ATRP (seATRP), [31][32][33] light in photo-induced ATRP (photo-ATRP), [34,35] or mechanical forces in mechanically induced ATRP (mechano-ATRP) [36] and in ultrasonication-induced ATRP (sono-ATRP) can be applied. [37,38] Electrochemistry offers additional opportunity to catalyst recycle, [18,39] eliminates needs for chemical reducing agents, [40] provides temporal control during the process, [27] and extends polymerization to aqueous media.…”

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).…”

Low Ppm Atom Transfer Radical Polymerization in (Mini)Emulsion Systems

“…One of the main disadvantages of these methods was the necessity for high catalyst concentrations loading, which was improved by the addition of an additional redox cycle, thus decreasing the catalyst concentration to a "low ppm" level [12][13][14][15]. The development of "low ppm" ATRP techniques [16] comprise an activator regeneration by electron transfer (ARGET) ATRP [17][18][19][20], initiator for continuous activator regeneration (ICAR) ATRP [21][22][23][24], supplemental activators and reducing agents (SARA) ATRP [25][26][27][28][29], and external stimuli induced approaches-mechanically induced ATRP (mechano-ATRP) [30,31], photoinitiated ATRP (photo-ATRP) [32][33][34][35], electrochemically mediated ATRP (eATRP) [36][37][38][39][40][41][42], ultrasonication-induced ATRP (sono-ATRP) [5,43] and metal-free ATRP [44][45][46] (Scheme 1).…”

“…However, generating stable miniemulsion droplets requires high energy input during the sonication process, limiting its broad application in many scale-up productions in the industry [74]. The miniemulsion polymerization is a versatile technique for the formation of a broad range of structured materials as linear or branched polymers with predetermined molecular weight and low dispersity [34,38,43].…”