Coenzyme-Catalyzed Electro-RAFT Polymerization

Here we report an electrochemically switchable reversible addition–fragmentation chain transfer polymerization (<i>e</i>RAFT). A new family of biochemical coenzymes are discovered that can be used as highly efficient electroredox catalysts to mediate this polymerization. The oxidation of coenzyme, nicotinamide adenine dinucleotide (NADH), can promote the reduction of a chain transfer agent, triggering generation and propagation of polymer radicals. External potential can activate the reduction of the NAD⁺ oxidized state and pause the propagation. Tuning the applied potential to reversibly switch the catalyst between its reduced and oxidized states can toggle the polymerization between ON and OFF states. This new strategy is universal to a broad scope of monomers, and ppm-level coenzymes result in the desirable polymer structures with targeted molecular weight, dispersity, and excellent chain-end fidelity. We envisage that the bioorganic-based catalysts would open new directions of organocatalyzed electro-controlled polymerization and be of value in electrocatalysis for well-structured polymers

CO₂‑Switchable Supramolecular Block Glycopolypeptide Assemblies

A novel supramolecular block glycopolypeptide, designed to have the viral building blocks and be sensitive to CO₂, a physiological stimulus, was prepared via the orthogonal coupling of two end-functionalized biopolymers, dextran with β-cyclodextrin terminal (Dex-CD) and poly­(l-valine) with a benzimidazole tail (BzI-PVal), respectively, driven by the end-to-end host–guest interactions. Due to the CO₂-cleavable CD/BzI connection, both the vesicular and fibrous aggregates of this supramolecular block copolymer self-assembled in aqueous solution can undergo a reversible process of disassembly upon “breathing in” CO₂ and assembly upon “breathing out” CO₂, which mimics, to some extent, the disintegration and construction of viral capsid nanostructures

Pulsating Polymer Micelles via ATP-Fueled Dissipative Self-Assembly

Energy dissipation underlies dynamic behaviors of the life system. This principle of biology is explicit, but its in vitro mimic is very challenging. Here we use an energy-dissipative self-assembly pathway to create a life-like polymer micellar system that can do periodic and self-adaptive pulsating motion fueled by cell energy currency, adenosine triphosphate (ATP). Such a micelle expansion–contraction behavior relies on transient supramolecular interactions between the micelle and ATP fuel. The micelles capturing ATPs will deviate away from the thermodynamic equilibrium state, driving a continuous micellar expansion that temporarily breaks the amphiphilic balance, until a competing ATP hydrolysis consumes energy to result in an opposing micellar contraction. As long as ATP energy is supplied to keep the system in out-of-equilibrium, this reciprocating process can be sustained, and the ATP level can orchestrate the rhythm and amplitude of nanoparticulate pulsation. The man-made assemblies provide a model for imitating biologically time-dependent self-assembly and periodic nanocarriers for programmed drug delivery

Reversible Self-Assembly of Supramolecular Vesicles and Nanofibers Driven by Chalcogen-Bonding Interactions

Chalcogen-bonding interactions have been viewed as new non-covalent forces in supra­molecular chemistry. However, harnessing chalcogen bonds to drive molecular self-assembly processes is still unexplored. Here we report for the first time a novel class of supra-amphiphiles formed by Te···O or Se···O chalcogen-bonding interactions, and their self-assembly into supra­molecular vesicles and nanofibers. A quasi-calix[4]­chalcogena­diazole (C4Ch) as macrocyclic donor and a tailed pyridine <i>N</i>-oxide surfactant as molecular acceptor are designed to construct the donor–acceptor complex via chalcogen–chalcogen connection between the chalcogena­diazole moieties and oxide anion. The affinity of such chalcogen-bonding can dictate the geometry of supra-amphiphiles, driving diverse self-assembled nanostructures. Furthermore, the reversible disassembly of these structures can be promoted by introducing competing halide ions or by decreasing systemic pH

Light-Initiated <i>in Situ</i> Self-Assembly (LISA) from Multiple Homopolymers

Almost all of polymeric nanostructures are now prepared by a classical post-self-assembly strategy. An ambitious target is to quest new polymer <i>in situ</i> self-assembly ways. Here we pose a <i>light-initiated in situ self-assembly</i> method, named LISA, which can <i>de novo</i> form various nanostructures through orthogonal photoligation from multiple homopolymers. Tuning the initial componential or light parameter, one can predict and govern the systematic morphological evolution. This method circumvents tedious synthesis and solution-processing procedures of block copolymers in post-self-assembly strategy and allows the preparation of ordered assemblies from simple homopolymers in one-pot photoreaction. We anticipate that this photocontrolled <i>in situ</i> self-assembly strategy would provide a new vision for facile construction of high-ordered nanostructures starting from homopolymer

Therapeutic-Ultrasound-Triggered Shape Memory of a Melamine-Enhanced Poly(vinyl alcohol) Physical Hydrogel

Therapeutic-ultrasound-triggered shape memory was demonstrated for the first time with a melamine-enhanced poly­(vinyl alcohol) (PVA) physical hydrogel. The addition of a small amount of melamine (up to 1.5 wt %) in PVA results in a strong hydrogel due to the multiple H-bonding between the two constituents. A temporary shape of the hydrogel can be obtained by deformation of the hydrogel (∼65 wt % water) at room temperature, followed by fixation of the deformation by freezing/thawing the hydrogel under strain, which induces crystallization of PVA. We show that the ultrasound delivered by a commercially available device designed for the patient’s pain relief could trigger the shape recovery process as a result of ultrasound-induced local heating in the hydrogel that melts the crystallized PVA cross-linking. This hydrogel is thus interesting for potential applications because it combines many desirable properties, being mechanically strong, biocompatible, and self-healable and displaying the shape memory capability triggered by a physiological stimulus

Access to <i>N</i>‑Aryl (Iso)quinolones via Aryne-Induced Three-Component Coupling Reaction

N-Aryl (iso)quinolones are of increasing interest in material and medicinal chemistry, although general routes for their provision remain underexplored, especially when compared with its N-alkyl counterparts. Herein, we report a modular and transition-metal-free, aryne-induced three-component coupling protocol that allows the facile synthesis of structurally diverse N-aryl (iso)quinolones from readily accessible halo-(iso)quinolines in the presence of water. Preliminary results highlight the applicability of our method through scale-up synthesis, downstream derivatization, and flexible synthesis involving other types of aryne precursors

Peroxynitrite (ONOO^–) Redox Signaling Molecule-Responsive Polymersomes

Designing specific-responsive polymer nanocapsules toward a definite cell signaling molecule for targeted therapy faces a great challenge. Here we demonstrate that new block copolymer appended trifluoromethyl ketone side groups can chemoselectively respond to an endogenous redox biosignal, peroxynitrite (ONOO^–), but shield the interference of other biogenic reactive oxygen, nitrogen, and sulfur species (ROS/RNS/RSS). The ONOO^– signaling molecule is capable of triggering cascade oxidation–elimination reactions to cleave the side functionalities from the polymer chain, which induces a large alteration of the polymer amphiphilicity and further leads to controllable disassembly of their self-assembled vesicular structure. Modulating the ONOO^– stimulus concentrations could readily control the vesicle dissociation rates for desirable drug delivery. We envisage that this polymer model would provide a new scenario to construct bioresponsive macromolecular systems for future biomedical nanotechnologies

Sequential Block Copolymer Self-Assemblies Controlled by Metal–Ligand Stoichiometry

While numerous efforts have been devoted to developing easy-to-use probes based on block copolymers for detecting analytes due to their advantages in the fields of self-assembly and sensing, a progressive response on block copolymers in response to a continuing chemical event is not readily achievable. Herein, we report the self-assembly of a 4-piperazinyl-1,8-naphthalimide based functional block copolymer (PS-<i>b</i>-PN), whose self-assembly and photophysics can be controlled by the stoichiometry-dependent metal–ligand interaction upon the side chain. The work takes advantages of (1) stoichiometry-controlled coordination–structural transformation of the piperazinyl moiety on PS-<i>b</i>-PN toward Fe³⁺ ions, thereby resulting in a shrinkage–expansion conversion of the self-assembled nanostructures in solution as well as in thin film, and (2) stoichiometry–controlled competition between photoinduced electron transfer and spin–orbital coupling process upon naphthalimide fluorophore leading to a boost–decline emission change of the system. Except Fe³⁺ ions, such a stoichiometry-dependent returnable property cannot be observed in the presence of other transition ions. The strategy for realizing the dual-channel sequential response on the basis of the progressively alterable nanomorphologies and emissions might provide deeper insights for the further development of advanced polymeric sensors

CO-Signaling Molecule-Responsive Nanoparticles Formed from Palladium-Containing Block Copolymers

The overproduction of cell-signaling molecules causes various human diseases. This intrinsic feature offers a biochemical basis to design biosignal-responsive nanocarriers for cell-selective therapy. Here we develop a new palladium-containing block copolymer, which can chemoselectively respond to carbon monoxide (CO)―a crucial gaseous signaling molecule in cellswhile inhibiting disturbances from other endogenous analogues. Palladium is introduced into polymer for the first time, and such an organopalladium-connected chain can be cleaved by a CO-induced cascade insertion–elimination reaction, triggering a desirable disassembly of their self-assembling micelles. The micellar dissociation rate depends on the dose of CO stimulus. We envisage that this polymer model would enrich the repertoire of metallopolymers and provide a new platform for designing signaling molecule-responsive macromolecular systems