1,720,989 research outputs found
Polymer Brushes on Nanoparticles for Controlling the Interaction with Protein-Rich Physiological Media
No full textThe interaction of nanoparticles (NPs) with biological environments triggers the formation of a protein corona (PC), which significantly influences their behavior in vivo. This review explores the evolving understanding of PC formation, focusing on the opportunity for decreasing or suppressing protein-NP interactions by macromolecular engineering of NP shells. The functionalization of NPs with a dense, hydrated polymer brush shell is a powerful strategy for imparting stealth properties in order to elude recognition by the immune system. While poly(ethylene glycol) (PEG) has been extensively used for this purpose, concerns regarding its stability and immunogenicity have prompted the exploration of alternative polymers. The stealth properties of brush shells can be enhanced by tailoring functionalities and structural parameters, including the molar mass, grafting density, and polymer topology. Determining correlations between these parameters and biopassivity has enabled us to obtain polymer-grafted NPs with high colloidal stability and prolonged circulation time in biological media
Electrochemical approaches for better understanding of atom transfer radical polymerization
No full textElectrochemistry strongly contributed to deepen the understanding and predictability of atom transfer radical polymerization (ATRP) outcomes. Several electrochemical tools have been used to determine thermodynamic and kinetic parameters that are hardly accessible by other techniques. The electrochemical methods presented in this brief review were applied to systems with extremely different ATRP reactivity, providing a rational database of primary reference for further developments of ATRP
Why Do We Need More Active ATRP Catalysts?
No full textAtom transfer radical polymerization (ATRP) is a staple technique for the preparation of polymers with well-defined architecture. In ATRP, the catalyst governs the equilibrium between propagating radicals and dormant species, thus affecting the polymerization control for a range of monomers and transferable atoms employed in the process. The design and the use of highly active catalysts could diminish the amount of transition metal complexes, extend ATRP to less active monomers and give access to new chain-end functionalities. At the same time, very active catalysts can be involved in formation of organometallic species. Herein, the role of the catalyst on the ATRP equilibrium is carefully elucidated, together with recent observations on the impact of the catalyst nature on formation of organometallic species and relevant side reactions. Based on this knowledge, a perspective on the benefits and challenges that derive from the use of highly active ATRP catalysts is presented
Atom Transfer Radical Polymerization: Billion Times More Active Catalysts and New Initiation Systems
No full textApproaching 25 years since its invention, atom transfer radical polymerization (ATRP) is established as a powerful technique to prepare precisely defined polymeric materials. This perspective focuses on the relation between structure and activity of ATRP catalysts, and the consequent choice of the initiating system, which are paramount aspects to well-controlled polymerizations. The ATRP mechanism is discussed, including the effect of kinetic and thermodynamic parameters and side reactions affecting the catalyst. The coordination chemistry and activity of copper complexes used in ATRP are reviewed in chronological order, while emphasizing the structure–activity correlation. ATRP-initiating systems are described, from normal ATRP to low ppm Cu systems. Most recent advancements regarding dispersed media and oxygen-tolerant techniques are presented, as well as future opportunities that arise from progressively more active catalysts and deeper mechanistic understanding
Polymer Chemistry for Improving Lithium Metal Anodes
No full textLithium metal anode based rechargeable batteries (LMBs) are regarded as a highly appealing alternatives to replace state-of-the-art lithium ion batteries (LIBs) for applications that demand higher energy density. Due to the highly reactive nature of metallic lithium and the related challenges with regard to dendrite issues at the anode, and electrolyte and cathode design, the industrial success of LMBs is yet to be safely achieved. Traditionally, in an LMB, the role of polymeric components is mostly limited to separators and cathode binders. With the advancement in polymer chemistry and its growing applications in materials science, it is now recognized that functional polymers can greatly improve the practical performance of an LMB. This paper discusses some representative studies, in order to demonstrate how various macromolecular approaches could be adopted to improve LMBs especially concerning the anode side, including electrolyte and artificial solid electrolyte interphase
Photoinduced atom transfer radical polymerization in ab initio emulsion
No full textAtom transfer radical polymerization (ATRP) performed in ab initio emulsion provides access to well-defined polymers in a low-cost, eco-friendly environment. Herein, photoinduced ab initio emulsion ATRP of various (meth)acrylate monomers is reported. The polymerization rate increased with the solubility of the monomer in water. Well-controlled (co)polymerizations were achieved under violet light and low catalyst loading, even in an open-to-air system through enzymatic degassing
Ab Initio Emulsion Atom-Transfer Radical Polymerization
No full textStable latexes of poly(meth)acrylates with predetermined molecular weights, narrow molecular-weight distributions, and controlled architecture were prepared by true ab initio emulsion atom-transfer radical polymerization. Water-soluble (macro)initiators in combination with a hydrophilic catalyst, Cu/tris(2-pyridylmethyl)amine, initiated the polymerization in the aqueous phase. The catalyst strongly interacted with the surfactant sodium dodecyl sulfate (SDS), thereby tuning the polymerization within nucleated hydrophobic polymer particles. Long-term stable latexes were obtained, even with SDS loading below 3 wt % relative to monomer. Block and gradient copolymers were prepared in situ. The reaction volume and solid content were successfully increased to 100 mL and 40 vol %, respectively, thus suggesting facile scale-up of this technique. The proposed setup could be integrated in existing industrial plants used for emulsion polymerization
Redox-switchable atom transfer radical polymerization
No full textTemporal control in atom transfer radical polymerization (ATRP) relies on modulating the oxidation state of a copper catalyst, as polymer chains are activated by L/CuI and deactivated by L/CuII. (Re)generation of L/CuI activator has been achieved by applying a multitude of external stimuli. However, switching the Cu catalyst off by oxidizing to L/CuII through external chemical stimuli has not yet been investigated. A redox switchable ATRP was developed in which an oxidizing agent was used to oxidize L/CuI activator to L/CuII, thus halting the polymerization. A ferrocenium salt or oxygen were used to switch off the Cu catalyst, whereas ascorbic acid was used to switch the catalyst on by (re)generating L/CuI. The redox switches efficiently modulated the oxidation state of the catalyst without sacrificing control over polymerization
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