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

Photocontrolled atom transfer radical polymer-ization-induced self-assembly (PhotoATR-PISA) mediated by UV light (lambda = 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) (POEG-MA) 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.