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Smart, multi-stimuli-responsive nanogels that possess dynamic covalent bonds (DCBs) exhibit reversibility under equilibrium conditions allowing for controlled disassembly and release of cargo. These nanomaterials have innumerable applications in areas including drug delivery, sensors, soft actuators, smart surfaces, and environmental remediation. In this work, we implement one-pot, photo-controlled atom transfer radical polymerization-induced self-assembly (PhotoATR-PISA), mediated by UV light (λ = 365 nm) and parts per million (ppm) levels (ca. <20 ppm) of a copper(II) bromide catalyst, to fabricate dual crosslinked, polymeric nanogels with tunable orthogonal reversible covalent (TORC-NGs) core-crosslinks (CCLs). These TORC-NGs were crosslinked efficiently via coumarin photodimerization which occured simultaneously during polymerization using coumarin-functionalized methacrylate crosslinkers (CouMA). At the same time, crosslinking of nanocarriers with N,N-cystamine bismethacrylamide (CBMA) introduced orthogonal, redox-responsive, disulfide CCLs. Furthermore, incorporation of poly(glycidyl methacrylate) (PGMA) core-forming segments provided a simple handle for switchable solubility through acid-catalyzed ring-opening hydrolysis of pendant epoxide groups. In this way, the kinetics of release were tailored by the pH of the surrounding media. Thus, these TORC-NG systems showed coupled pH-, redox- and photo-responsive controlled release and disassembly behavior with full release of cargo only observed in the right sequence of stimuli and only when all three are utilized. The multi-stimuli-responsive nature of these TORC-NGs was successfully utilized herein for the controlled encapsulation and on-demand AND-gate release of hydrophobic Nile Red fluorescent reporters used as drug simulants. Various TORC-NG morphologies were synthesized in this report including nanosphere, worm-like and tubesome NGs showing variable release characteristics. 

Introducing facile regenerability into adsorbent materials can potentially increase sustainability in water treatment systems enabled by extended use. Herein, we detail our recent syntheses of dynamic nanostructured worm-gel materials and their implementation as regenerable adsorbents for water treatment. Photo-controlled atom transfer radical polymerization-induced self-assembly (PhotoATR-PISA) was employed to synthesize various polymer nanostructures, including dispersed spheres, worms, and vesicles, and nanostructured worm-gels, via the synthesis and simultaneous in situ assembly of BAB triblock copolymers. Two dynamic, disulfide-functionalized macroinitiators (SS-MI-1 and 2)with different degree of polymerization and one nondynamic macroinitiator (CC-MI) were synthesized via polymerization of oligo(ethylene glycol methyl ether methacrylate) (OEGMA). PhotoATR-PISA was then implemented via the chain extension fromSS-MI-1, 2 and CC-MI with glycidyl methacrylate (GMA) or benzyl methacrylate (BMA) forming BAB-type triblock copolymer nanoparticles in situ. The final morphology in PhotoATR-PISA was influenced not only by conventional factors such as solids content and block DP but also by unimer exchange rates yielding arrested, nanostructured worm-gels in many instances and arrested vesicle-gels in one instance. These PISA-gel materials were implemented as adsorbents for phenanthrene, a model compound registered as a priority pollutant by the US EPA, from aqueous solutions. The chemical tunability of these materials enabled enhanced, targeted removal of phenanthrene facilitated by π−π interactions, as evidenced by the increased adsorption capacities of PBMA-based PISA-gels when compared to PGMA. Furthermore, the dynamicity of disulfide worm-gels (SS-WG) enabled disulfide exchange-induced regeneration stimulated by UV light. This UV-responsive exchange was investigated for POEGMA macroinitiators as well as dissolved triblock copolymers, dispersed nanoparticles, and SS-WG materials. Finally, the regenerability of the PNT-saturated SS-WG adsorbents induced by UV irradiation (λ = 365 nm) was examined and compared with control worm-gels absent of disulfides, demonstrating enhanced recovery of adsorption capacity under mild irradiation conditions.