Chain Extensions in PhotoATRP-Induced Self-Assembly (PhotoATR-PISA): A Route to Ultrahigh Solids Concentrations and Click Nanoparticle Networks as Adsorbents for Water Treatment

Abstract

Photocontrolled atom transfer radical polymerization-induced self-assembly (PhotoATR-PISA) mediated by UV light (λ = 365 nm) was utilized to obtain polymer nanostructures with variable morphologies, including nanospheres, wormlike micelles, and vesicles, at ambient temperature by using parts per million (ppm) levels (ca. < 20 ppm) of copper catalyst. Using Cu­(II)­Br2/tris­(pyridin-2-ylmethyl)­amine (TPMA) catalyst systems and functional ATRP initiators, we performed PhotoATR-PISA all in one-pot via sequential chain extension starting from solvophilic poly­(oligo­(ethylene glycol) methyl ether methacrylate) (POEGMA) macroinitiator growth followed by PISA using different proportions of glycidyl methacrylate (GMA) and/or benzyl methacrylate (BMA) core-forming blocks forming alkyne-functional polymer nanoparticles. Remarkably, multiple, iterative chain extensions were accomplished introducing additional GMA and BMA monomers in multiple steps without additional solvent leading to stable nanoparticle dispersions with record-high final solid concentrations of 63 and 79 wt %, respectively. Core cross-linked nanoparticles (CCL NPs) were synthesized by incorporating N,N-cystamine bismethacrylamide (CBMA) cross-linkers in later stage chain extensions providing a route to CCL nanoworms. Furthermore, introducing BMA and GMA in varying orders sequentially allowed for the synthesis of sequence-controlled gradient copolymers, though this had limited effects on nanoparticle morphology. Finally, utilizing the copper­(I)-catalyzed azide–alkyne cycloaddition (CuAAC) click reactions between alkyne-functionalized NPs and bisazide, telechelic poly­(ethylene glycol) (PEG), nanostructured networks were fabricated consisting of nanospherical, beaded worm, nanoworm, and vesicle morphologies. The interstitial porosity of these ClickNP networks allows them to be potent adsorbents with explored applications in water treatment demonstrated via the rapid uptake of phenanthrene pollutants from aqueous solutions.

Dynamic Worm-Gel Materials as Tunable, Regenerable Adsorbents for Water Treatment

“…To investigate the scope of morphologies possible for BABtriblock PhotoATR-PISA, various microscopy techniques, PGMA copolymers in PhotoATR-PISA. 21,22 For PISA7−12 synthesized with SS-MI-2 (POEGMA 34 ), the morphological evolution progressed from beaded worms and culminated in the formation of nanostructured SS-WGs for target DP PGMA = 300 at both SC % (Figure 2c,d). For PISA10−12 (SC % = 25%), however, the trend diverged slightly, transitioning through entangled worm cluster dispersions at DP PGMA = 200 prior to SS-WG formation at DP PGMA = 300.…”

Multi-responsive nanogels with tunable orthogonal reversible covalent (TORC) core-crosslinks for AND-gate controlled release

“…Firstly, the alkyne-functionalized ATRP initiator was synthesized based on a previous report 70 via the esterification of 2-bromoisobutyryl bromide with propargyl alcohol. These alkyne-functionalities decorate TORC-NGs with reactive groups which will be utilized in future applications such as attaching receptors for targeted drug delivery and performing inter-nanoparticle crosslinking reactions to generate porous hydrogels for tissue engineering.…”

“…Prior to use, oligo(ethylene oxide) methyl ether methacrylate (OEGMA, M n = 300 Da, Sigma-Aldrich), benzyl methacrylate (BMA; Alfa Aesar), and glycidyl methacrylate (GMA; Alfa Aesar) were passed through a column of basic alumina to remove inhibitor. Synthesis of CBMA, 56 CouMA (SI) 69 and alkyne-ATRP initiator 70 was adapted from previously reported literature.…”

“…To synthesize higher order worm-like TORC-NGs, our previously demonstrated sequential chain extension strategy was applied. 70 In brief, the procedure outlined above was repeated up until the adding of GMA. Prior to addition of crosslinkers, one initial batch of degassed GMA (7.53 mmol, 1.0 mL, 86 eq.…”

“…To access these morphologies, we altered the core-forming segments from PGMA to PBMA due to our previous difficulties in forming higher-order morphologies using PGMA alone (Scheme S1 †). 70 Furthermore, we performed PhotoATR-PISA in two pots, starting with macroinitiator synthesis and purification prior to PISA to allow for more precise control to hydrophililc/lipophilic ratios. The morphology evolved slowly due to the presence of CBMA at the start of the PhotoATR-PISA reaction and the gradual polymerization of this crosslinker.…”