In-situ nitroxide-mediated radical polymerization (NMP) processes: their understanding and optimization

Morphology and Emulsification of Poly(N-2-(methacryloyloxy) ethyl pyrrolidone)-b-poly(benzyl methacrylate) Assemblies by Polymerization-Induced Self-Assembly

In this work, a series of amphiphilic diblock copolymers poly(N-2-(methacryloyloxy) ethyl pyrrolidone)-b-poly(benzyl methacrylate) (PNMP m -b-PBzMA n ) were developed by the dispersion polymerization method in ethanol. The polymerization-induced self-assembly (PISA) behaviors were studied systematically, and a comprehensive structure-property relationship was also established. Two distinct PISA tendencies were observed, which was mainly depended on the polymerization degree m of PNMP segment. When m is small such as 39 and 55, morphological transitions from spherical to vesicle-like assemblies via wormlike ones upon increasing n commonly happen regardless of the solid content. Alternatively, spherical assemblies became the sole morphology for PNMP64-b-PBzMA n block copolymers because of the excellent solvophilicity of the PNMP64 segment. Attributing to the amphiphilicity of PNMP m -b-PBzMA n block copolymers, PNMP m -b-PBzMA n assemblies by PISA are a type of excellent Pickering emulsifiers. These assemblies prefer to stabilize O/W Pickering emulsions as confirmed by the confocal laser scanning microscopy method, and the effects of polymerization degree of PBzMA segment or morphologies of PNMP m -b-PBzMA n assemblies are finite.

Ferrocene-Modified Polyacrylonitrile-Containing Block Copolymers as Preceramic Materials

In the pursuit of fabricating functional ceramic nanostructures, the design of preceramic functional polymers has garnered significant interest. With their easily adaptable chemical composition, molecular structure, and processing versatility, these polymers hold immense potential in this field. Our study succeeded in focusing on synthesizing ferrocene-containing block copolymers (BCPs) based on polyacrylonitrile (PAN). The synthesis is accomplished via different poly(acrylonitrile-block-methacrylate)s via atom transfer radical polymerization (ATRP) and activators regenerated by electron transfer ATRP (ARGET ATRP) for the PAN macroinitiators. The molecular weights of the BCPs range from 44 to 82 kDa with dispersities between 1.19 and 1.5 as determined by SEC measurements. The volume fraction of the PMMA block ranges from 0.16 to 0.75 as determined by NMR. The post-modification of the BCPs using 3-ferrocenyl propylamine has led to the creation of redox-responsive preceramic polymers. The thermal stabilization of the polymer film has resulted in stabilized morphologies based on the oxidative PAN chemistry. The final pyrolysis of the sacrificial block segment and conversion of the metallopolymer has led to the formation of a porous carbon network with an iron oxide functionalized surface, investigated by scanning electron microscopy (SEM), energy dispersive X-ray mapping (EDX), and powder X-ray diffraction (PXRD). These findings could have significant implications in various applications, demonstrating the practical value of our research in convenient ceramic material design.

Iron-Catalyzed, Light-Driven Decarboxylative Alkoxyamination

An iron-catalyzed visible-light driven decarboxylative alkoxyamination is disclosed. In the presence of FeBr2 and TEMPO, a large array of carboxylic acids including marketed drugs and biobased molecules is turned into the corresponding alkoxyamine derivatives. The versatility of the latter offers an entry towards molecular diversity generation from abundant starting materials and catalyst. Overall, this method proposes a unified and general approach for LMCT-based iron-catalyzed decarboxylative functionalization.

Stimuli-sensitive polymer prodrug nanocarriers by reversible-deactivation radical polymerization

Polymer prodrugs are based on the covalent linkage of therapeutic molecules to a polymer structure which avoids the problems and limitations commonly encountered with traditional drug-loaded nanocarriers in which drugs are just physically entrapped (e.g., burst release, poor drug loadings). In the past few years, reversible-deactivation radical polymerization (RDRP) techniques have been extensively used to design tailor-made polymer prodrug nanocarriers. This synthesis strategy has received a lot of attention due to the possibility of fine tuning their structural parameters (e.g., polymer nature and macromolecular characteristics, linker nature, physico-chemical properties, functionalization, etc.), to achieve optimized drug delivery and therapeutic efficacy. In particular, adjusting the nature of the drug-polymer linker has enabled the easy synthesis of stimuli-responsive polymer prodrugs for efficient spatiotemporal drug release. In this context, this review article will give an overview of the different stimuli-sensitive polymer prodrug structures designed by RDRP techniques, with a strong focus on the synthesis strategies, the macromolecular architectures and in particular the drug-polymer linker, which governs the drug release kinetics and eventually the therapeutic effect. Their biological evaluations will also be discussed.

Synthesis of Polymeric Mimics of Ice-Binding Proteins

Cobalt-mediated radical polymerization (CMRP) enables the preparation of both short and long polymers from acrylic and vinyl ester monomers with low dispersity. Here we describe the synthesis, purification, and characterization of polymeric mimics of ice-binding proteins based on the water-soluble polymer poly(vinyl alcohol) by CMRP. Block copolymers of poly(vinyl alcohol) and poly(acrylic acid) were prepared from the precursor copolymers poly(vinyl acetate)-b-poly(acrylonitrile) upon hydrolysis. Copolymers comprising up to hundreds of monomers and dispersities Mw/Mn < 1.3 were produced by this method.

Evaluating polymeric biomaterials to improve next generation wound dressing design

Wound healing is a dynamic series of interconnected events with the ultimate goal of promoting neotissue formation and restoration of anatomical function. Yet, the complexity of wound healing can often result in development of complex, chronic wounds, which currently results in a significant strain and burden to our healthcare system. The advancement of new and effective wound care therapies remains a critical issue, with the current therapeutic modalities often remaining inadequate. Notably, the field of tissue engineering has grown significantly in the last several years, in part, due to the diverse properties and applications of polymeric biomaterials. The interdisciplinary cohesion of the chemical, biological, physical, and material sciences is pertinent to advancing our current understanding of biomaterials and generating new wound care modalities. However, there is still room for closing the gap between the clinical and material science realms in order to more effectively develop novel wound care therapies that aid in the treatment of complex wounds. Thus, in this review, we discuss key material science principles in the context of polymeric biomaterials, provide a clinical breadth to discuss how these properties affect wound dressing design, and the role of polymeric biomaterials in the innovation and design of the next generation of wound dressings.

Two-Dimensional Black Phosphorus: Preparation, Passivation and Lithium-Ion Battery Applications

As a new type of single element direct-bandgap semiconductor, black phosphorus (BP) shows many excellent characteristics due to its unique two-dimensional (2D) structure, which has great potential in the fields of optoelectronics, biology, sensing, information, and so on. In recent years, a series of physical and chemical methods have been developed to modify the surface of 2D BP to inhibit its contact with water and oxygen and improve the stability and physical properties of 2D BP. By doping and coating other materials, the stability of BP applied in the anode of a lithium-ion battery was improved. In this work, the preparation, passivation, and lithium-ion battery applications of two-dimensional black phosphorus are summarized and reviewed. Firstly, a variety of BP preparation methods are summarized. Secondly, starting from the environmental instability of BP, different passivation technologies are compared. Thirdly, the applications of BP in energy storage are introduced, especially the application of BP-based materials in lithium-ion batteries. Finally, based on preparation, surface functionalization, and lithium-ion battery of 2D BP, the current research status and possible future development direction are put forward.

Thiol-Lactam Initiated Radical Polymerization (TLIRP): Scope and Application for the Surface Functionalization of Nanoparticles

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Controlled polymerization techniques make the possible fabrication of polymers with desired molecular weights, narrow dispersity, and tailor-making of advanced hybrid materials. Thiol- Lactam Initiated Radical Polymerization (TLIRP) was introduced in 2002 and developed during the last two decades. The thiol/lactam combination enables one to generate radicals that can initiate the polymerization of vinyl-based monomers. The study of the mechanism and kinetics of TLIRP revealed the characteristics of living polymerization for TLIRP. Moreover, TLIRP has been used successfully for the synthesis of homopolymers, block copolymers, and statistical copolymers with polydispersity below 2.0. Especially, TLIRP provides a very straightforward method for grafting polymer brushes on the surface of nanoparticles. We review herein the systems developed for TLIRP and their applications for macromolecular engineering, emphasizing the surface functionalization of nanoparticles via the grafting-from approach.

Redox Monitoring in Nuclear Medical Imaging

Significance: The imbalance in redox homeostasis is known as oxidative stress, which is relevant to many diseases such as cancer, arteriosclerosis, and neurodegenerative disorders. Overproduction of reactive oxygen species (ROS) is one of the factors that trigger the redox state imbalance in vivo. The ROS have high reactivity and impair biomolecules, whereas antioxidants and antioxidant enzymes, such as ascorbate and glutathione, reduce the overproduction of ROS to rectify the redox imbalance. Owing to this, redox monitoring tools have been developed to understand the redox fluctuations in oxidative stress-related diseases. Recent Advances: In an attempt to monitor redox substances, including ROS and radical species, versatile modalities have been developed, such as electron spin resonance, chemiluminescence, and fluorescence. In particular, many fluorescent probes have been developed that are selective for ROS. This has significantly contributed to understanding the relevance of ROS in disease onset and progression. Critical Issues: To date, the dynamics of ROS and radical fluctuation in in vivo redox states remain unclear, and there are a few methods for the in vivo detection of redox fluctuations. Future Directions: In this review, we summarize the development of radiolabeled probes for monitoring redox-relevant species by nuclear medical imaging that is applicable in vivo. In the future, translational research is likely to be advanced through the development of highly sensitive and in vivo applicable detection methods, such as nuclear medical imaging, to clarify the underlying dynamics of ROS, radicals, and redox substances in many diseases. Antioxid. Redox Signal. 36, 797-810.

Probing polymer brushes with electrochemical impedance spectroscopy: a mini review

Polymer brushes are frequently used as surface-tethered antifouling layers in biosensors to improve sensor surface-analyte recognition in the presence of abundant non-target molecules in complex biological samples by suppressing nonspecific interactions. However, because brushes are complex systems highly responsive to changes in their surrounding environment, studying their properties remains a challenge. Electrochemical impedance spectroscopy (EIS) is an emerging method in this context. In this mini review, we aim to elucidate the potential of EIS for investigating the physicochemical properties and structural aspects of polymer brushes. The application of EIS in brush-based biosensors is also discussed. Most common principles employed in these biosensors are presented, as well as interpretation of EIS data obtained in such setups. Overall, we demonstrate that the EIS-polymer brush pairing has a considerable potential for providing new insights into brush functionalities and designing highly sensitive and specific biosensors.

Miktoarm Star Copolymers Prepared by Transformation from Enhanced Spin Capturing Polymerization to Nitroxide-Mediated Polymerization (ESCP-Ŧ-NMP) toward Nanomaterials

Reversible-deactivation radical polymerization (RDRP) serves as a powerful tool nowadays for the preparations of unique linear and non-linear macromolecules. In this study, enhanced spin capturing polymerizations (ESCPs) of styrene (St) and tert-butyl acrylate (tBA) monomers were, respectively, conducted in the presence of difunctional (1Z,1'Z)-1,1'-(1,4-phenylene) bis (N-tert-butylmethanimine oxide) (PBBN) nitrone. Four-arm (PSt)4 and (PtBA)4 star macroinitiators (MIs) can be afforded. By correspondingly switching the second monomer (i.e., tBA and St), miktoarm star copolymers (μ-stars) of (PSt)2-μ-(PtBA-b-PSt)2 and (PtBA)2-μ-(PSt-b-PtBA)2) were thus obtained. We further conducted hydrolysis of the PtBA segments to PAA (i.e., poly(acrylic acid)) in μ-stars to afford amphiphilic μ-stars of (PSt)2-μ-(PAA-b-PSt)2 and (PAA)2-μ-(PSt-b-PAA)2. We investigated each polymerization step and characterized the obtained two sets of "sequence-isomeric" μ-stars by FT-IR, 1H NMR, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). Interestingly, we identified their physical property differences in the case of amphiphilic μ-stars by water contact angle (WCA) and atomic force microscopy (AFM) measurements. We thus proposed two microstructures caused by the difference of polymer chain sequences. Through this polymerization transformation (Ŧ) approach (i.e., ESCP-Ŧ-NMP), we demonstrated an interesting and facile strategy for the preparations of μ-stars with adjustable/switchable interior and exterior polymer structures toward the preparations of various nanomaterials.

Recent Advances in bis-Chalcone-Based Photoinitiators of Polymerization: From Mechanistic Investigations to Applications

Over the past several decades, photopolymerization has become an active research field, and the ongoing efforts to develop new photoinitiating systems are supported by the different applications in which this polymerization technique is involved-including dentistry, 3D and 4D printing, adhesives, and laser writing. In the search for new structures, bis-chalcones that combine two chalcones' moieties within a unique structure were determined as being promising photosensitizers to initiate both the free-radical polymerization of acrylates and the cationic polymerization of epoxides. In this review, an overview of the different bis-chalcones reported to date is provided. Parallel to the mechanistic investigations aiming at elucidating the polymerization mechanisms, bis-chalcones-based photoinitiating systems were used for different applications, which are detailed in this review.

Modern trends in controlled synthesis of functional polymers: fundamental aspects and practical applications

Major trends in controlled radical polymerization (CRP) or reversible-deactivation radical polymerization (RDRP), the most efficient method of synthesis of well-defined homo- and copolymers with specified parameters and properties, are critically analyzed. Recent advances associated with the three classical versions of CRP: nitroxide mediated polymerization, reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization, are considered. Particular attention is paid to the prospects for the application of photoinitiation and photocatalysis in CRP. This approach, which has been intensively explored recently, brings synthetic methods of polymer chemistry closer to the light-induced processes of macromolecular synthesis occurring in living organisms. Examples are given of practical application of CRP techniques to obtain industrially valuable, high-tech polymeric products.

The bibliography includes 429 references.

Responsive Polymer Brush Design and Emerging Applications for Nanotheranostics

Responsive polymer brushes are a category of polymer brushes that are capable of conformational and chemical changes in response to external stimuli. They offer unique opportunities for the control of bio-nano interactions due to the precise control of chemical and structural parameters such as the brush thickness, density, chemistry, and architecture. The design of responsive brushes at the surface of nanomaterials for theranostic applications has developed rapidly. These coatings can be generated from a very broad range of nanomaterials, without compromising their physical, photophysical, and imaging properties. Although the use of responsive brushes for nanotheranostic remains in its early stages, in this review, the aim is to present how the systems developed to date can be combined to control sensing, imaging, and controlled delivery of therapeutics. The recent developments for such design and associated methods for the synthesis of responsive brushes are discussed. The responsive behaviors of homo polymer brushes and brushes with more complex architectures are briefly reviewed, before the applications of responsive brushes as smart delivery systems are discussed. Finally, the recent work is summarized on the use of responsive polymer brushes as novel biosensors and diagnostic tools for the detection of analytes and biomarkers.

Spirocyclic Nitroxides as Versatile Tools in Modern Natural Sciences: From Synthesis to Applications. Part I. Old and New Synthetic Approaches to Spirocyclic Nitroxyl Radicals

Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at a-, b-, or g-carbon atom of the nitroxide fragment, which is part of the heterocyclic system. Despite the fact that the first representatives of SNRs were obtained about 50 years ago, the methodology of their synthesis and their usage in chemistry and biochemical applications have begun to develop rapidly only in the last two decades. Due to the presence of spiro-function in the SNRs molecules, the latter have increased stability to various reducing agents (including biogenic ones), while the structures of the biradicals (SNBRs) comprises a rigid spiro-fused core that fixes mutual position and orientation of nitroxide moieties that favors their use in dynamic nuclear polarization (DNP) experiments. This first review on SNRs will give a glance at various strategies for the synthesis of spiro-substituted, mono-, and bis-nitroxides on the base of six-membered (piperidine, 1,2,3,4-tetrahydroquinoline, 9,9'(10H,10H')-spirobiacridine, piperazine, and morpholine) or five-membered (2,5-dihydro-1H-pyrrole, pyrrolidine, 2,5-dihydro-1H-imidazole, 4,5-dihydro-1H-imidazole, imidazolidine, and oxazolidine) heterocyclic cores.

N-Heterocyclic carbene-carbodiimide (NHC-CDI) betaine adducts: synthesis, characterization, properties, and applications

N-Heterocyclic carbenes (NHCs) are an important class of reactive organic molecules used as ligands, organocatalysts, and σ-donors in a variety of electroneutral ylide or betaine adducts with main-group compounds. An emerging class of betaine adducts made from the reaction of NHCs with carbodiimides (CDIs) form zwitterionic amidinate-like structures with tunable properties based on the highly modular NHC and CDI scaffolds. The adduct stability is controlled by the substituents on the CDI nitrogens, while the NHC substituents greatly affect the configuration of the adduct in the solid state. This Perspective is intended as a primer to these adducts, touching on their history, synthesis, characterization, and general properties. Despite the infancy of the field, NHC-CDI adducts have been applied as amidinate-type ligands for transition metals and nanoparticles, as junctions in zwitterionic polymers, and to stabilize distonic radical cations. These applications and potential future directions are discussed.

Collective radical oligomerisation induced by an STM tip on a silicon surface

Over the past decade, on-surface fabrication of organic nanostructures has been widely investigated for the development of molecular electronic components, catalysts, and new materials. Here, we introduce a new strategy to obtain alkyl oligomers in a controlled manner using on-surface radical oligomerisations that are triggered by electrons between the tip of a scanning tunnelling microscope and the Si(111)√3 ×√3 R30°-B surface. This electron transfer event only occurs when the bias voltage is below -4.5 V and allows access to reactive radical species under exceptionally mild conditions. This transfer can effectively 'switch on' a sequence leading to the formation of oligomers of defined size distribution thanks to the on-surface confinement of the reactive species. Our approach enables new ways to initiate and control radical oligomerisations with tunnelling electrons, leading to molecularly precise nanofabrication.

One-pot synthesis for gradient copolymers via concurrent tandem living radical polymerization: mild and selective transesterification of methyl acrylate through Al(acac)3 with common alcohols

The acrylate based gradient copolymers were successfully synthesized by concurrent tandem living radical polymerization using Al(acac)₃ as cocatalyst with common alcohols.

Aluminum Tralen Complex Meditated Reversible-Deactivation Radical Polymerization of Vinyl Acetate

The Al^III(tralen)Cl complex (tralenH₂ = N,N'-di(cyclohepta-2,4,6-trien-1-one-2-yl)-1,2-diaminobenzene) has been synthesized and applied to mediate the reversible-deactivation radical polymerization (RDRP) of vinyl monomers. The polymerization of unconjugated monomers such as vinyl acetate (VAc) and N-vinylpyrrolidone (NVP) with Al^III(tralen)Cl showed the living characters of linearly increased molecular weight with conversion and formation of block copolymer. However, the control manners in the polymerization of conjugated monomers like acrylates and styrene were limited. The electron paramagnetic resonance (EPR) spectrum indicated that Al^III(tralen)BArF (BArF = tetrakis(3,5-trifluormethylphenyl)borate) and propagating radicals formed a paramagnetic dormant species, possibly PVAc-Al^III(tralen)BArF, via the single-electron transfer to the tralen ligand.

Multiple biological active 4-aminopyrazoles containing trifluoromethyl and their 4-nitroso-precursors: Synthesis and evaluation

4-Nitroso-3-trifluoromethyl-5-alkyl[(het)aryl]pyrazoles were synthesized via one-pot nitrosation of 1,3-diketones or their lithium salts followed by treatment of hydrazines. Reduction of nitroso-derivatives made it possible to obtain 4-amino-3-trifluoromethylpyrazoles chlorides. According to computer-aided calculations, all synthesized compounds are expected to have acceptable ADME profile for drug design. Tuberculostatic, antibacterial, antimycotic, antioxidant and cytotoxic activities of the compounds were evaluated in vitro, while their analgesic and anti-inflammatory action was tested in vivo along with acute toxicity studies. N-Unsubstituted 4-nitrosopyrazoles were the most effective tuberculostatics (MIC to 0.36 μg/ml) and antibacterial agents against Streptococcus pyogenes (MIC to 7.8 μg/ml), Staphylococcus aureus,S. aureus MRSA and Neisseria gonorrhoeae (MIC to 15.6 μg/ml). 4-Nitroso-1-methyl-5-phenylpyrazole had the pronounced antimycotic action against a wide range of fungi (Trichophytonrubrum, T. tonsurans, T. violaceum, T. interdigitale, Epidermophytonfloccosum, Microsporumcanis with MIC 0.38-12.5 μg/ml). N-Unsubstituted 4-aminopyrazoles shown high radical-scavenging activity in ABTS test, ORAC/AAPH and oxidative erythrocyte hemolysis assays. 1-Methyl-5-phenyl-3-trifluoromethylpyrazol-4-aminium chloride revealed potential anticancer activity against HeLa cells (SI > 1351). The pronounced analgesic activity was found for 4-nitroso- and 4-aminopyrazoles having phenyl fragment at the position 5 in "hot plate" test. The most of the obtained pyrazoles had a moderate acute toxicity.

New Variants of Nitroxide Mediated Polymerization

Nitroxide-mediated polymerization is now a mature technique, at 35 years of age. During this time, several variants have been developed: enhanced spin capture polymerization (ESCP), photoNMP (NMP2), chemically initiated NMP (CI-NMP), spin label NMP (SL-NMP), and plasmon-initiated NMP (PI-NMP). This mini-review is devoted to the features and applications of these variants.

Recent Advances in Hybrid Biomimetic Polymer-Based Films: from Assembly to Applications

Biological membranes, in addition to being a cell boundary, can host a variety of proteins that are involved in different biological functions, including selective nutrient transport, signal transduction, inter- and intra-cellular communication, and cell-cell recognition. Due to their extreme complexity, there has been an increasing interest in developing model membrane systems of controlled properties based on combinations of polymers and different biomacromolecules, i.e., polymer-based hybrid films. In this review, we have highlighted recent advances in the development and applications of hybrid biomimetic planar systems based on different polymeric species. We have focused in particular on hybrid films based on (i) polyelectrolytes, (ii) polymer brushes, as well as (iii) tethers and cushions formed from synthetic polymers, and (iv) block copolymers and their combinations with biomacromolecules, such as lipids, proteins, enzymes, biopolymers, and chosen nanoparticles. In this respect, multiple approaches to the synthesis, characterization, and processing of such hybrid films have been presented. The review has further exemplified their bioengineering, biomedical, and environmental applications, in dependence on the composition and properties of the respective hybrids. We believed that this comprehensive review would be of interest to both the specialists in the field of biomimicry as well as persons entering the field.

An N-Heterocyclic-Carbene-Derived Distonic Radical Cation

We present the discovery of a novel radical cation formed through one-electron oxidation of an N-heterocyclic carbene-carbodiimide (NHC-CDI) zwitterionic adduct. This compound possesses a distonic electronic structure (spatially separate spin and charge regions) and displays persistence under ambient conditions. We demonstrate its application in a redox-flow battery exhibiting minimal voltage hysteresis, a flat voltage plateau, high Coulombic efficiency, and no performance decay for at least 100 cycles. The chemical tunability of NHCs and CDIs suggests that this approach could provide a general entry to redox-active NHC-CDI adducts and their persistent radical ions for various applications.

Photo-induced copper mediated copolymerization of activated-ester methacrylate polymers and their use as reactive precursors to prepare multi-dentate ligands for the water transfer of inorganic nanoparticles

Polymers bearing activated ester groups are synthesized using photo-ATRP and used as precursors for direct synthesis of multi-phosphonic acid functionalized ligands which are able to transfer different nanoparticles with distinct cores into water.

Tailoring polymer dispersity and shape of molecular weight distributions: methods and applications

The width and shape of molecular weight distributions can significantly affect the properties of polymeric materials and thus are key parameters to control. This mini-review aims to critically summarise recent approaches developed to tailor molecular weight distributions and highlights the strengths and limitations of each technique. Special emphasis will also be given to applications where tuning the molecular weight distribution has been used as a strategy to not only enhance polymer properties but also to increase the fundamental understanding behind complex mechanisms and phenomena.