Oxygen-demanding Photocontrolled RAFT Polymerization under Ambient Conditions

Integrating Metabolic Oligosaccharide Engineering and SPAAC Click Chemistry for Constructing Fibrinolytic Cell Surfaces

To effectively solve the problem of significant loss of transplanted cells caused by thrombosis during cell transplantation, this study simulates the human fibrinolytic system and combines metabolic oligosaccharide engineering with strain-promoted azide-alkyne cycloaddition (SPAAC) click chemistry to construct a cell surface with fibrinolytic activity. First, a copolymer (POL) of oligoethylene glycol methacrylate (OEGMA) and 6-amino-2-(2-methylamido)hexanoic acid (Lys) was synthesized by reversible addition-fragmentation chain transfer (RAFT) copolymerization, and the dibenzocyclooctyne (DBCO) functional group was introduced into the side chain of the copolymer through an active ester reaction, resulting in a functionalized copolymer DBCO-PEG4-POL with ε-lysine ligands. Then, azide functional groups were introduced onto the surface of HeLa model cells through metabolic oligosaccharide engineering, and DBCO-PEG4-POL was further specifically modified onto the surface of HeLa cells via the SPAAC "click" reaction. In vitro investigations revealed that compared with unmodified HeLa cells, modified cells not only resist the adsorption of nonspecific proteins such as fibrinogen and human serum albumin but also selectively bind to plasminogen in plasma while maintaining good cell viability and proliferative activity. More importantly, upon the activation of adsorbed plasminogen into plasmin, the modified cells exhibited remarkable fibrinolytic activity and were capable of promptly dissolving the primary thrombus formed on their surfaces. This research not only provides a novel approach for constructing transplantable cells with fibrinolytic activity but also offers a new perspective for effectively addressing the significant loss of transplanted cells caused by thrombosis.

Organoboron-mediated polymerizations

The scientific community has witnessed extensive developments and applications of organoboron compounds as synthetic elements and metal-free catalysts for the construction of small molecules, macromolecules, and functional materials over the last two decades. This review highlights the achievements of organoboron-mediated polymerizations in the past several decades alongside the mechanisms underlying these transformations from the standpoint of the polymerization mode. Emphasis is placed on free radical polymerization, Lewis pair polymerization, ionic (cationic and anionic) polymerization, and polyhomologation. Herein, alkylborane/O2 initiating systems mediate the radical polymerization under ambient conditions in a controlled/living manner by careful optimization of the alkylborane structure or additives; when combined with Lewis bases, the selected organoboron compounds can mediate the Lewis pair polymerization of polar monomers; the bicomponent organoboron-based Lewis pairs and bifunctional organoboron-onium catalysts catalyze ring opening (co)polymerization of cyclic monomers (with heteroallenes, such as epoxides, CO2, CO, COS, CS2, episulfides, anhydrides, and isocyanates) with well-defined structures and high reactivities; and organoboranes initiate the polyhomologation of sulfur ylides and arsonium ylides providing functional polyethylene with different topologies. The topological structures of the produced polymers via these organoboron-mediated polymerizations are also presented in this review mainly including linear polymers, block copolymers, cyclic polymers, and graft polymers. We hope the summary and understanding of how organoboron compounds mediate polymerizations can inspire chemists to apply these principles in the design of more advanced organoboron compounds, which may be beneficial for the polymer chemistry community and organometallics/organocatalysis community.

Photo Fenton RAFT Polymerization of (Meth)Acrylates in DMSO Sensitized by Methylene Blue

A novel open-to-air photo RAFT polymerization of a series of acrylate and methacrylate monomers mediated by matching chain transfer agent irradiated by far-red light in DMSO is reported. Hydroxyl radical (•OH) generated from methylene blue (MB) sensitized decomposition of H2 O2 via photo-Fenton like-reaction is used for polymerization initiation. The "living/control" characteristic is evidenced by kinetic study, in which a pseudo first order curve and linearly increases of molecular weight with the increase of monomer conversion are observed. The living end-group fidelity is characterized by MALDI-TOF-MS and 1 H NMR results, and confirmed by successful chain extension. The temporary controllability is proved by light on/off switch experiment.

Simple and Rapid Adhesion of Commodity Polymer Substrates under Ambient Conditions Using Complexed Alkylboranes

Adhesives are ubiquitous in manufacturing spanning nearly all sectors from healthcare and photovoltaics to aerospace and electronics. Yet many commercial polymers remain challenging to adhere, necessitating either pretreatment, mechanical fastening, or adhesive processes that involve specialized equipment, high temperature/vacuum, and long cure times. Thus, rapid-cure adhesives for polymers that can set under ambient conditions using simple procedures are desirous because they offer cost savings, faster production, and greater design freedom to producers. Herein, we report a powerful adhesive platform that bonds a wide scope of commodity polymers via (hydrogen) atom transfer and free-radical (graft) polymerization initiated with a trialkylborane-ligand complex and isocyanate decomplexing agent. The developed adhesive formulation is air-stable, bulk, and operates in air at room temperature using a high-glass-transition temperature polyacrylate, i.e., poly(isobornyl acrylate). The alkylborane-initiated bonding process is rapid (∼30 min), requires minimal surface preparation (cleaning and mild roughening), and successfully bonds seven diverse substrates including polytetrafluoroethylene, polyethylene, polypropylene, polycarbonate, nylon, polymethylmethacrylate, and polyvinylchloride. This contribution uniquely investigates the process-property relationships for the adhesive formulation, lap-shear performance, mechanism of failure, and a reactive additive for enhancing the adhesive's glass-transition temperature to ∼120 °C (polyhedral oligomeric silsesquioxane or POSS) to widen its operation temperature. We envision that the reported alkylborane-initiated adhesion platform could hold promise in the automotive, aerospace, and marine sectors as means for rapid manufacturing and structural adhesion.