Star Polymers

Controlled synthesis of β-cyclodextrin-based starlike helical poly(phenyl isocyanide) and its application in chiral resolution

In an effort to expand the diversity of helical polymers exhibiting intricate structures, a strategy for the precise fabrication of β-cyclodextrin-based star polymers adorned with helical poly(phenyl isocyanide) (PPI) arms has been successfully realized through the integration of isocyanide polymerization and atom transfer radical polymerization (ATRP). An elegant β-cyclodextrin embellished with 7 Pd(II) complexes on one side and 14 bromine groups on the other side, denoted as ((Pd(II))7-CD-(Br)14), was initially synthesized. Subsequently, the (PPI)7-CD-(Br)14 was synthesized through the polymerization of the phenyl isocyanide monomer initiated with (Pd(II))7-CD-(Br)14. Finally, starlike PPI was obtained by ATRP of 1,2-diacrylyl ethane initiated via the macro-initiator of (PPI)7-CD-(Br)14. Circular dichroism measurement analysis indicated that the obtained starlike PPI exhibited a consistent helical conformation with a preferred handedness, and it was revealed that the helical structure of starlike PPI originated from the PPI backbone, rather than intermolecular aggregation in solutions. Furthermore, the starlike PPI demonstrated excellent efficacy in the chiral resolution of racemic compounds, achieving an enantiomeric excess (e.e.) of 92 % for threonine racemates when used as a chiral resolution agent.

Harnessing nanoparticles and bioorthogonal chemistries for improving precision of nuclear medicine

The convergence of nanotechnology, radiopharmaceutical development and molecular imaging has unveiled exciting opportunities for the progress of innovative diagnostic and therapeutic strategies, paving the way for significant advancements in biomedical research, especially in relation to cancer. For example, the use of highly sensitive and quantitative nuclear imaging techniques including PET and SPECT, together with nanoparticles for tumour imaging and therapy has recently expanded rapidly. While the long circulating properties of many nanomaterials are beneficial for prodrug chemotherapy formulations, due to the constant decay processes involved in nuclear medicines, directly labelled materials result in prolonged systemic radiation exposure and reduced therapeutic indices due to the unfavourable target-to-background ratios. This is due to the tendency for long circulating nanomaterials to distribute within the blood to other organs, such as the liver and spleen. The recent integration of bioorthogonal chemistry with nanotechnology and molecular imaging/radiotherapy has revolutionized the field by allowing the decoupling of the targeting molecule (i.e. nanomaterial with a bioorthogonal tag) and the imaging/therapeutic radioisotope. In this way, the detection/therapeutic element can be administered as a secondary "chase" molecule that contains the bioorthogonal partner, thereby creating an avenue to improve therapeutic index and provide imaging and treatments with reduced risk. This review will provide an overview of the progress made thus far in the field of nuclear imaging and radiotherapy for cancer using the combination of nanomaterials and bioorthogonal chemistry. We also provide a critical evaluation of the challenges and opportunities for using these approaches to better understand disease and treatment mechanisms, with the potential for downstream clinical translation.

Cyclodextrin-Initiated N-Carboxyanhydride Polymerization for the Design of Stereostructural Dobby Polypeptides with Jellyfish-Type Architecture

Strict criteria of biomedical materials in synthesis efficiency, structure determinacy, and biological safety pose formidable challenges for the synthesis of dobby polypeptides. Herein we reported a cyclodextrin (CD)-initiated, 1,1,3,3-Tetramethylguanidine (TMG)-catalyzed one-step N-carboxyanhydride (NCA) ring-opening polymerization (ROP) strategy to synthesize a series of dobby polypeptides that fulfill the criteria of biomedical materials. By leveraging TMG's catalytic mechanisms in nucleophilicity enhancement for CD hydroxyl groups and active center creation for NCA monomers, this strategy achieves efficient NCA polymerization within 2 hours and high monomer conversion up to 93.5 %. Meticulous characterizations illustrate that CD-centric polypeptides present jellyfish-type stereochemical structures, in which the arm number, length, orientation and initiation sites are precisely determined. Simultaneously, CD-centric polypeptides possess excellent self-assembling capacities to guide nanostructure fabrication, exhibiting broad-spectrum small-molecule drug encapsulation. Additionally, natural CD applied in multipoint initiation of core-first NCA ROP fundamentally improves the biodegradability and biosafety of dobby polypeptides, thus facilitating their biomedical applications.

Harnessing interfacial entropic effects in polymer grafted nanoparticle composites for tailoring their thermo-mechanical and separation properties

Nanocomposites based on polymeric materials have been extensively studied to understand and control the thermodynamics, flow, and mechanical properties of the underlying matrix as well to create new materials with diverse optical, electrical, magnetic, separation, catalytic, and biomedical properties. In the form of thin films or membranes, such materials can impart remarkable improvements in various properties of the underlying substrates. Using nanoparticles with grafted polymer chains usually overcomes a major hurdle in achieving enhancements in various properties by enabling better dispersion in the matrix while at the same time introducing a new parameter - interfacial entropy - leading to the emergence of new parameter space for tuning dispersion, flow and thermal properties. In this article, we highlight how this interfacial entropic effect can be harnessed to control various properties in thin films and membranes of grafted nanoparticle composites, in particular their thermo-mechanical properties, viscosity, fragility, glass transition temperature (Tg), and dynamic heterogeneity as well as their ability to act as highly selective gas separation and water desalination membranes. We discuss the application of a range of experimental techniques as well as molecular dynamics simulation to extract these properties and obtain microscopic insight into how the interplay of various surface and interfacial effects lies at the centre of these significant property improvements and enhanced functionality. Finally, we provide an outlook on future opportunities for designing sustainable PNCs, emphasizing their potential in environmental, energy, and biomedical applications, with advanced experiments and modelling driving further innovations.

Tumor-Targeting Theranostic Polymers

Theranostic polymers have emerged as a versatile platform in cancer nanomedicine, integrating therapeutic and imaging functionalities to overcome challenges in oncology. Featuring diverse architectures such as linear polymers, dendrimers, star-like polymers, and bottle-brush polymers, these systems enable tumor-targeted drug delivery, real-time imaging, and controlled release. Recent advances in stimuli-responsive designs and biomimetic strategies have improved their specificity, stability, and adaptability, outperforming conventional nanocarriers. This review summarizes the design, synthesis, and biomedical applications of theranostic polymers, focusing on their potential to address tumor heterogeneity and biological barriers. The challenges of biocompatibility, immunogenicity, and clinical translation are discussed, with a perspective toward future developments in precision medicine and imaging-guided cancer therapy.

Single-molecule resolution of macromolecules with nanopore devices

Nanopore-based electrical detection technology holds single-molecule resolution and combines the advantages of high sensitivity, high throughput, rapid analysis, and label-free detection. It is widely applied in the determination of organic and biological macromolecules, small molecules, and nanomaterials, as well as in nucleic acid and protein sequencing. There are a wide variety of organic polymers and biopolymers, and their chemical structures, and conformation in solution directly affect their ensemble properties. Currently, there is limited approach available for the analysis of single-molecule conformation and self-assembled topologies of polymers, dendrimers and biopolymers. Nanopore single-molecule platform offers unique advantages over other sensing technologies, particularly in molecular size differentiation of macromolecules and complex conformation analysis. In this review, the classification of nanopore devices, including solid-state nanopores (SSNs), biological nanopores, and hybrid nanopores is introduced. The recent developments and applications of nanopore devices are summarized, with a focus on the applications of nanopore platform in the resolution of the structures of synthetic polymer, including dendritic, star-shaped, block copolymers, as well as biopolymers, including polysaccharides, nucleic acids and proteins. The future prospects of nanopore sensing technique are ultimately discussed.

Synthesis of Star Polymers with Ultrahigh Molecular Weights and Tunable Dispersities via Photoiniferter Polymerization

Simultaneous control over macromolecular chain topology, molecular weight, and dispersity is an important synthetic goal in polymer chemistry. The synthesis of well-defined poly(methyl acrylate) star polymers with ultrahigh molecular weights (>106 g mol-1) and tunable dispersities is realized for the first time via blue light-controlled photoiniferter polymerization using a tetrafunctional switchable RAFT agent (SRA4). The spectroscopic properties and polymerization activity of SRA4 can be reversibly tuned by addition of acid/base. For example, protonation of SRA4 with 4-toluenesulfonic acid (TsOH) leads to enhanced UV-visible light absorption, a faster polymerization rate, and a lower dispersity for the resulting star polymer. Star polymers were prepared with predicted molecular weights (Mn ≈ 80-1550 kg mol-1) and tunable dispersities (Đ ≈ 1.8-1.2) when targeting degrees of polymerization in the range of 1000-20000 in the presence of varying amounts of TsOH. High end-group fidelity for such star polymers was confirmed by one-pot chain extension experiments, which afforded a series of pseudoblock copolymers with controlled dispersities. Finally, rotational rheology was used to examine the effect of molecular weight, dispersity, and chain topology (whether linear or star-shaped) on solution viscosity.

Chromenylium Star Polymers: Merging Water Solubility and Stealth Properties with Shortwave Infrared Emissive Fluorophores

Fluorescence imaging in the shortwave infrared (SWIR) region has emerged as a vital tool for studying mammals. SWIR emissive polymethine dyes are well-suited to this endeavor; however, advancing in vivo imaging utility with these dyes is primarily limited by hydrophobicity and/or nonspecific protein association. Herein, we take a distinct approach to combine hydrophilicity and stealth behavior to construct bright, SWIR emissive chromenylium fluorophores by employing a well-defined poly(2-methyl-2-oxazoline) (POx) star polymer architecture, which we refer to as chromenylium stars, or "CStars." Of these polymer-shielded dyes, the variant containing five POx chains (CStar30) boasts particularly enhanced aqueous solubility and SWIR brightness, enabling high-resolution SWIR imaging in mice. The swift renal clearance and stealth behavior displayed in vivo also achieves improved noninvasive visualization of the lymphatic system. Further, CStar's orthogonal biodistribution to an FDA-approved dye, indocyanine green (ICG), facilitates excitation-multiplexed SWIR imaging in two colors to achieve simultaneous visualization of both fluid dynamics and protein dynamics in the same animal in real time at video-rate frame counts.

Construction of UCST-Responsive Claw-Like Polysulfobetaines for Efficient Capture of Cellulase

The high cost of enzymatic glycolysis has seriously restricted the industrialization of lignocellulose-based sugar platform technology. Recovering and recycling cellulase can reduce the cost. Here, a thermo-responsive claw-type polysulfobetaine (PSPA) was constructed for hydrophobic grasping and efficient recycling of cellulase. Compared with the linear sulfobetaine homopolymer (PSPE), PSPA had more sensitive temperature response and strong cellulase recovery ability. PSPE-3 (Mw=355.1 kDa) was added to the hydrolysis system of corncob residue (CCR) (50 °C), at 0.4 mass ratio of PSPE-3 to cellulase, and after enzymatic hydrolysis, 50 % of the cellulase was saved when cooling to 25 °C. But only 0.05 times PSPA-1 (Mw=30.0 kDa) was added to the CCR system, and 70 % of the cellulase was saved when cooling to 25 °C. This work presents a claw shaped protein-capture agent, polysulfobetaine for capturing cellulase, which is of great significance to reduce the lignocellulosic hydrolysis cost, and efficiently separate enzyme proteins.

Varying the Core Topology in All-Glycidol Hyperbranched Polyglycerols: Synthesis and Physical Characterization

In the present study, low molecular weight cyclic polyglycidol is used as a macroinitiator for hypergrafting glycidol and producing cyclic graft hyperbranched polyglycerol (cPG-g-hbPG) in the molecular weight range of 103-106 g mol-1. Linear graft hyperbranched polyglycerol (linPG-g-hbPG) and hyperbranched polyglycerol (hbPG) are prepared as reference samples. This creates a family of hbPG structures with cyclic, linear, and star cores, allowing to evaluate their properties in solution and in bulk. The morphology study of the high molecular weight structures using atomic force microscopy revealed a spherical shape for cPG-g-hbPG and hbPG, and a cylindrical shape for linPG-g-hbPG in the nanometric range. Small angle X-ray scattering confirmed the compact particle-like structure of this family of hbPG architectures. Interestingly, the glass transition temperature showed a structure dependence, with cPG-g-hbPG having the highest values and hbPG having the lowest values for the same molecular weight. This study is a step forward in the generation of water-soluble polymers with tailored structure and functionality for advanced applications.

Mineral Plastics and Gels from Multi-Arm Ionomers

Plastic production and waste are a growing menace that affects the soil, the marine environment, and the air in a cumulative manner. The demand for mineral and bioplastics from renewable and biodegradable materials has therefore increased in all relevant sectors. The use of currently available degradable plastics is, however, limited by their poor mechanical properties and high production costs. In addition, many of today's plastics undergo uncontrolled biodegradation processes that involve harsh or expensive conditions and which may last from months to years. Here, the advantages of using multi-arm polymers for the production of sustainable mineral plastics are presented. A 4-arm poly(acrylic acid) is synthesized via atom transfer radical polymerization and is reacted with divalent calcium ions to obtain semi-liquid hydrogel or degradable plastic when dried. The mechanical properties of the different phases are evaluated and compared with linear poly(acrylic acid) of the same molecular weight. The multi-arm approach yielded improved mechanical characteristics, including self-healing and biodegradation without compromising other typical hydrogel characteristics. This concept of synthesizing multi-arm polymers with improved characteristics from building blocks of traditionally linear structures may be applicable to other mineral and bioplastic materials including acrylates, polysaccharides, and DNA.

Self-Diffusion of Star and Linear Polyelectrolytes in Salt-Free and Salt Solutions

This work explored solution properties of linear and star poly(methacrylic acids) with four, six, and eight arms (LPMAA, 4PMAA, PMAA, and 8PMAA, respectively) of matched molecular weights in a wide range of pH, salt, and polymer concentrations. Experimental measurements of self-diffusion were performed by fluorescence correlation spectroscopy (FCS), and the results were interpreted using the scaling theory of polyelectrolyte solutions. While all PMAAs were pH sensitive and showed an increase in hydrodynamic radius (R h) with pH in the dilute regime, the R h of star polymers (measured at basic pH values) was significantly smaller for the star polyacids due to their more compact structure. Fully ionized star PMAAs were also found to be less sensitive to changes in salt concentration and type of the counterion compared to linear PMAA. While R h of fully ionized linear PMAA decreased in the series Li+ > Na+ > K+ > Cs+ in agreement with the Hofmeister series, R h of star PMAAs was virtually independent of type of the counterion for eight-arm PMAA. However, molecular architecture strongly affected interactions of counterions with PMAAs. In particular, 7Li NMR revealed that the spin-lattice relaxation time T 1 of Li+ ions in low-salt solutions of eight-arm PMAA was ∼2-fold smaller than that in the solution of linear PMAA, suggesting slower Li+-ion dynamics within star polymers. An increase in concentration of monovalent chloride salts, c s, above that of the PMAA monomer unit concentration (c m) resulted in shrinking of both linear and star molecules, with the hydrodynamic size R h scaling as R h ∝ c s -0.11±0.01. Self-diffusion of linear and star polyelectrolytes was then studied in a wide range of polyelectrolyte concentrations (10-3 mol/L < c m < 0.5 mol/L) in low-salt (<10-4 mol/L of added salt) and high-salt (1 mol/L) solutions. In both the low-salt and high-salt regimes, diffusion coefficient D was lower for PMAAs with a larger number of arms at a fixed c m. In addition, in both cases, D plateaued at low polymer concentrations and decreased at higher polymer concentrations. However, while in the high-salt conditions, the concentration dependence of D reflected transitions between the dilute to semidilute solution regimes as expected for neutral chains in good and theta solvents, analysis of the diffusion data in the low-salt conditions using the scaling theory revealed a different origin of the concentration dependence of D. Specifically, in the low-salt solutions, both linear and star PMAAs exhibited unentangled (Rouse-like) dynamics in the entire range of polyelectrolyte concentrations.

Robot-Assisted Synthesis of Structure-Controlled Star-Cluster Hydrogels with Targeted Mechanophysical Properties for Biomedical Applications

Advancements in polymer chemistry have enabled the design of macromolecular structures with tailored properties for diverse applications. Reversible addition-fragmentation chain-transfer (RAFT) polymerization is a controlled technique for precise polymer design. Automation tools further enhance polymer synthesis by enabling the rapid, reproducible preparation of polymer libraries. This study utilizes an automated platform and a biologically friendly bio-Fenton RAFT synthesis method to create hydrogels with embedded star polymers derived from complex block copolymers with controlled block lengths and sequences. Automation improves the efficiency compared to manual methods, while the choice of prepolymer and polymerization techniques ensures biocompatibility. Hydrogels formed by cross-linking linear block copolymers exhibit tunable physical, chemical, and mechanical properties. By systematically altering the prepolymer block sequences, promising hydrogel candidates for enhanced cell biocompatibility and proliferation are identified. These synthetic hydrogels mimic cellular microenvironments and offer a robust platform for biomedical applications, paving the way for an efficient hydrogel design and synthesis.

Cationic Star Polymers Obtained by the Arm-First Approach─Influence of Arm Number and Positioning of Cationic Units on Antimicrobial Activity

Recently, we published a study demonstrating the promising structure-activity relationship of 4-arm star polymers toward bacterial cells and biofilms. The aim of this study was to increase the number of arms to determine if this could further enhance activity via the arm-first approach, which enables access to star structures with a higher number of arms. A library of amphiphilic diblock and miktoarm star polymers was successfully synthesized, and their biological properties were assessed. The increased number of arms failed to increase activity for the diblock stars, possibly due to shielding of the cationic units located at the core from binding to the membrane, which was slightly improved for the miktoarm structures. However, the efficient synthesis of these structures shown herein could be used to synthesize star polymers with a higher cationic ratio or longer arms, thereby circumventing the limitation of reduced interaction of cationic units with the membrane.

The Whole Is Greater than the Sum of Its Parts - Challenges and Perspectives in Polyelectrolytes

Polyelectrolytes offer unique properties for biological applications due to their charged nature and high water solubility. Here, the challenges in their synthesis and characterization techniques are reviewed, emphasizing that their strong interactions with the surrounding media and counterions must be considered when working with this interesting class of materials. Their potential in complexation for gene delivery, their unique stealth and anti-fouling properties, and their more specific interactions with amino acid transporters for cancer therapy are highlighted. The underlying mechanisms responsible for their biological efficacy, including the proton sponge effect for endosomal release and their interactions with cellular membranes, are addressed. For polyelectrolytes with a high level of usage, an overview is given of their historical context. This Perspective outlines the potential of polyelectrolytes for innovative applications in the field of biomedicine. Considering the physicochemical characteristics of this class of materials, this work strives to elucidate the distinctive properties and applications of polyelectrolytes.

Metal-Coordinated Polymer-Inorganic Hybrids: Synthesis, Properties, and Application

This review examines the recent advancements and unique properties of polymer-inorganic hybrid materials formed through coordination bonding (Class II hybrids), which enable enhanced functionality and stability across various applications. Here, we categorize these materials based on properties gained through complexation, focusing on electrical conductivity, thermal stability, photophysical characteristics, catalytic activity, and nanoscale self-assembly. Two major synthetic approaches to making these hybrids include homogeneous and heterogeneous methods, each with distinct tradeoffs: Homogeneous synthesis is straightforward but requires favorable mixing between inorganic and polymer species, which are predominantly water-soluble complexes. In contrast, heterogeneous methods are post-processing techniques that provide high area selectivity for inorganic precursors, allowing precise integration within polymer matrices. Finally, we highlight the role of hybrid linkers, namely metallosupramolecular polymers, in creating structural diversity. These can be organized into three main groups: metal-organic frameworks (MOFs), coordination polymers (CPs), and supramolecular coordination complexes (SCCs). Each of these groups introduces unique structural and functional properties that expand the potential applications of hybrid materials.

Zinc Phthalocyanine Core-First Star Polymers Through Nitroxide Mediated Polymerization and Nitroxide Exchange Reaction

Nitroxide-mediated polymerization (NMP) and nitroxide exchange reaction (NER) are very efficient methodologies that require only suitable alkoxyamine derivatives and create different polymeric architectures in a controlled manner. Herein, the synthesis of star polymers containing TEMPO-substituted symmetric zinc phthalocyanine (ZnPc) is presented via NMP and NER. Moreover, linear polymer formation is conducted in a single arm on TEMPO-substituted asymmetric ZnPc to elucidate the properties of star polymers. All linear and star polymers are characterized by FT-IR, UV-vis, fluorescence, GPC, NMR, and EPR techniques. The results show that the proposed reactions are capable of forming controlled star-shaped polymers. The increasing arm number (from a single to four arms) results in variable dispersity values (Đ) (1.2-3) due to different arm lengths, especially in NMP. However, this difficulty has been overcome via NER, and star polymers have been successfully synthesized with relatively low molecular weight (30 K > 10 K) and low dispersity (1.2-1.9). The results clearly indicate that while styrene and 4-vinyl benzyl chloride monomers are introduced to the structure equally, star polymers with phthalocyanine can be synthesized in a controlled manner, and their quarternized derivatives have the potential to be effective as photoactive agents in photodynamic therapy.

Recent Advancements of Nanomedicine in Breast Cancer Surgery

Breast cancer surgery plays a pivotal role in the multidisciplinary approaches. Surgical techniques and objectives are gradually shifting from tumor complete resection towards prolonging survival, improving cosmetic outcomes, and restoring the social and psychological well-being of patients. However, surgical treatment still faces challenges such as inadequate sensitivity in sentinel lymph node localization, the need to improve intraoperative tumor boundary localization imaging, postoperative scar healing, and the risk of recurrence, necessitating other adjunct measures for improvement. To address these challenges, specificity-optimized nanomedicines have been introduced into the surgical therapeutic landscape of breast cancer. In particular, this review involves starting with an overview of breast structure and the composition of the tumor microenvironment and then introducing the guiding principle and foundation for the design of nanomedicine. Moreover, we will take the order process of breast cancer surgery diagnosis and treatment as the starting point, and adaptively propose the roles and advantages of nanomedicine in addressing the corresponding issues. Furthermore, we also involved the prospects of utilizing advanced technological approaches. Overall, this review seeks to uncover the sophisticated design and strategies of nanomedicine from a clinical standpoint, address the challenges faced in surgical treatment, and provide insights into this subject matter.

Redox-Active Water-Soluble Low-Weight and Polymer-Based Anolytes Containing Tetrazine Groups: Synthesis and Electrochemical Characterization

Polymer-based aqueous redox flow batteries (RFBs) are attracting increasing attention as a promising next-generation energy storage technology due to their potential for low cost and environmental friendliness. The search for new redox-active organic compounds for incorporation into polymer materials is ongoing, with anolyte-type compounds in high demand. In response to this need, we have synthesized and tested a range of new water-soluble redox-active s-tetrazine derivatives, including both low molecular weight compounds and polymers with different architectures. S-tetrazines are some of the smallest organic molecules that can undergo a reversible two-electron reduction in protic media, making them a promising candidate for anolyte applications. We have successfully modified linear polyacrylic acid and poly(N-isopropylacrylamide-co-acrylic acid) microgels with pendent 1,2,4,5-tetrazine groups. Electrochemical testing has shown that the new tetrazine-containing monomers and, importantly, the water-soluble redox polymers, both linear and microgel, demonstrate the chemical reversibility of the reduction process in an aqueous solution containing acetate buffer. This expands the range of water-soluble anodic materials suitable for water-based organic RFBs. The reduction potential value can be adjusted by changing the substituents in the tetrazine core. It is also worth noting that the choice of electrode material plays an important role in the kinetics of the tetrazine reaction: the use of carbon electrodes is particularly beneficial.

Janus Structure Construction of Polyester-Cotton Fabrics for Achieving Excellent Moisture, Moisture-Permeability, and Antibacterial Capability

Integration of hydrophobic and antibacterial functionalities into polyester-cotton blended (PTCO) textiles has attracted more attention but remains a challenge. Here, a Janus fabric with antibacterial effect, hydrophobicity, and enhanced moisture-permeability is fabricated using a "mist polymerization" approach. The PET fibers in the PTCO fabric are amino-functionalized through ammonolysis reactions of PET molecules with HDA, and mist treatments of poly lauryl methacrylate (PLMA) and poly(DMC-co-MA) (PDM) are applied on the two side surfaces of the PTCO-HDA fabric, respectively. The resulting Janus fabric exhibits an antibacterial rate of 99.9% against both E. coli and S. aureus, along with a hydrophobic property on its single side (PTCO-HDA@PLMA). Additionally, the establishment of a surface-free energy gradient across the fabric confers superior moisture-permeability to the Janus fabric, offering advantages in preserving textile comfort. Moreover, this approach does not significantly compromise the original fabric properties, such as mechanical strength, moisture permeability, and fabric softness. The proposed method offers a straightforward and scalable strategy for textile finishing, demonstrating great potential in expanding the application scope of PTCO fabrics, and it may hold a pivotal role in diverse applications, notably encompassing home textiles, wound dressings, and high-performance sportswear.

Star-polymer unimolecular micelle nanoparticles to deliver a payload across the blood-brain barrier

Nanocarrier-mediated therapeutic delivery to brain tissue is impeded by tightly controlled transportation across the blood-brain barrier (BBB). Herein, we report a well-defined core-shell star-shaped unimolecular micelle (star-UMM; a single polymer entity) as an efficient BBB-breaching nanoparticle for brain-specific administration of the fluorescent anticancer drug doxorubicin and in vivo mapping of brain tissues by the near-infrared biomarker IR780 in mice. The star-UMM was engineered by precisely programming the polymer topology having hydrophobic and hydrophilic polycaprolactone blocks and in-built with lysosomal enzyme-biodegradation stimuli to deliver the payloads at intracellular compartments. In vivo imaging in mice revealed prolonged circulation of star-UMM in blood for >72 h, and whole-organ image-quantification substantiated its efficient ability to breach the BBB. Star UMM exhibited excellent stability in blood circulation and reduced cardiotoxicity, was non-hemolytic, had substantial uptake in the cortical neurons of the mouse brain, had lysosomal enzymatic-biodegradation, and exhibited negligible immunogenicity or necrosis. This newly designed star-UMM could have long-term applications in brain-specific drug delivery.

Structural Engineering of Cationic Block Copolymer Architectures for Selective Breaching of Prokaryotic and Eukaryotic Biological Species

Positively charged antimicrobial polymers are known to cause severe damage to biological systems, and thus synthetic strategies are urgently required to design next-generation nontoxic cationic macromolecular architectures for healthcare applications. Here, we report a structural-engineering strategy to build cationic linear and star-block copolymer nanoarchitectures having identical chemical composition, molar mass, nanoparticle size, and positive surface charge, yet they differ distinctly in their biological action in breaching prokaryotic species such as E. coli (Gram-negative bacteria) without affecting eukaryotic species like red-blood and mammalian cells. For this purpose, linear and star-block structures are built on a polycaprolactone biodegradable platform having an imidazolium positive handle. Under physiological conditions, the linear architecture exhibits toxicity indiscriminately to all biological species, whereas its star counterpart is remarkably selective in membrane breaching action toward bacteria while maintaining inertness toward eukaryotic species. Confocal microscopy analysis of HPTS fluorescent dye-loaded star-polymer nanoparticles substantiated their antimicrobial action in E. coli. Tissue-penetrable near-infrared fluorescent dye (IR-780) loaded NP aided the in vivo biodistribution analysis and ex vivo quantification of cationic species' accumulations in vital organs in mice. Azithromycin, a clinical water-insoluble macrolide, is delivered from the star platform to accomplish synergistic antimicrobial activity by the combination of bactericidal-bacteriostatic action of the polymer carrier and drug together in a single system.

Phase-transformable metal-organic polyhedra for membrane processing and switchable gas separation

The capability of materials to interconvert between different phases provides more possibilities for controlling materials' properties without additional chemical modification. The study of state-changing microporous materials just emerged and mainly involves the liquefication or amorphization of solid adsorbents into liquid or glass phases by adding non-porous components or sacrificing their porosity. The material featuring reversible phases with maintained porosity is, however, still challenging. Here, we synthesize metal-organic polyhedra (MOPs) that interconvert between the liquid-glass-crystal phases. The modular synthetic approach is applied to integrate the core MOP cavity that provides permanent microporosity with tethered polymers that dictate the phase transition. We showcase the processability of this material by fabricating a gas separation membrane featuring tunable permeability and selectivity by switching the state. Compared to most conventional porous membranes, the liquid MOP membrane particularly shows the selectivity for CO2 over H2 with enhanced permeability.

Controlled Fabrication of Unimolecular Micelles as Versatile Nanoplatform for Multifunctional Applications

Unimolecular micelles (UMs) are nano-sized structures that are composed of single molecules with precise composition. Compared to self-assembled polymeric micelles, UMs possess ultra-stable property even in complex biological environment. With the development of controllable polymerization and coupling chemistry, the preparation of narrowly monodispersed UMs with precise morphology and size has been realized, which further facilitates their multifunctional applications. After brief introduction, state-of-the-art advances in the synthesis and applications of UMs are discussed with an emphasis on their bioapplications. It is believed that these UMs have great potential in future fabrication of multifunctional nanoplatforms.

Star-Like Polypeptides as Simplified Analogues of Horseradish Peroxidase (HRP) Metalloenzymes

Peroxidases, like horseradish peroxidase (HRP), are heme metalloenzymes that are powerful biocatalysts for various oxidation reactions. By using simple grafting-from approach, ring-opening polymerization (ROP), and manganese porphyrins, star-shaped polypeptides analogues of HRP capable of catalyzing oxidation reactions with H2O2 is successfully prepared. Like their protein model, these simplified analogues show interesting Michaelis-Menten constant (KM) in the mM range for the oxidant. Interestingly, the polymer structures are more resistant to denaturation (heat, proteolysis and oxidant concentration) than HRP, opening up interesting prospects for their use in catalysis or in biosensing devices.

Smart Galactosidase-Responsive Antimicrobial Dendron: Towards More Biocompatible Membrane-Disruptive Agents

Antimicrobial resistance is a global healthcare challenge that urgently needs the development of new therapeutic agents. Antimicrobial peptides and mimics thereof are promising candidates but mostly suffer from inherent toxicity issues due to the non-selective binding of cationic groups with mammalian cells. To overcome this toxicity issue, this work herein reports the synthesis of a smart antimicrobial dendron with masked cationic groups (Gal-Dendron) that could be uncaged in the presence of β-galactosidase enzyme to form the activated Enz-Dendron and confer antimicrobial activity. Enz-Dendron show bacteriostatic activity toward Gram-negative (P. aeruginosa and E. coli) and Gram-positive (S. aureus) bacteria with minimum inhibitory concentration values of 96 µm and exerted its antimicrobial mechanism via a membrane disruption pathway, as indicated by inner and outer membrane permeabilization assays. Crucially, toxicity studies confirmed that the masked prodrug Gal-Dendron exhibited low hemolysis and is at least 2.4 times less toxic than the uncaged cationic Enz-Dendron, thus demonstrating the advantage of masking the cationic groups with responsive immolative linkers to overcome toxicity and selectivity issues. Overall, this study highlights the potential of designing new membrane-disruptive antimicrobial agents that are more biocompatible via the amine uncaging strategy.

Analytical and Numerical Investigation of Star Polymers in Confined Geometries

The analysis of the impact of the star polymer topology on depletion interaction potentials, depletion forces, and monomer density profiles is carried out analytically using field theory methods and techniques as well as molecular dynamic simulations. The dimensionless depletion interaction potentials and the dimensionless depletion forces for a dilute solution of ideal star polymers with three and five legs (arms) in a Θ-solvent confined in a slit between two parallel walls with repulsive surfaces and for the case where one of the surfaces is repulsive and the other inert are obtained. Furthermore, the dimensionless layer monomer density profiles for ideal star polymers with an odd number (f˜ = 3, 5) of arms immersed in a dilute solution of big colloidal particles with different adsorbing or repelling properties in respect of polymers are calculated, bearing in mind the Derjaguin approximation. Molecular dynamic simulations of a dilute solution of star-shaped polymers in a good solvent with N = 901 (3 × 300 + 1 -star polymer with three arms) and 1501 (5 × 300 + 1 -star polymer with five arms) beads accordingly confined in a slit with different boundary conditions are performed, and the results of the monomer density profiles for the above-mentioned cases are obtained. The numerical calculation of the radius of gyration for star polymers with f˜ = 3, 5 arms and the ratio of the perpendicular to parallel components of the radius of gyration with respect to the wall orientation for the above-mentioned cases is performed. The obtained analytical and numerical results for star polymers with an odd number (f˜ = 3, 5) of arms are compared with our previous results for linear polymers in confined geometries. The acquired results show that a dilute solution of star polymer chains can be applied in the production of new functional materials, because the behavior of these solutions is strictly correlated with the topology of polymers and also with the nature and geometry of confined surfaces. The above-mentioned properties can find extensive practical application in materials engineering, as well as in biotechnology and medicine for drug and gene transmission.

Segregation kinetics of miktoarm star polymers: A dissipative particle dynamics study

We study the phase separation kinetics of miktoarm star polymer (MSP) melts/blends with diverse architectures using dissipative particle dynamics simulation. Our study focuses on symmetric and asymmetric miktoarm star polymer (SMSP/AMSP) mixtures based on arm composition and number. For a fixed MSP chain size, the characteristic microphase-separated domains initially show diffusive growth with a growth exponent ϕ∼1/3 for both melts that gradually crossover to saturation at late times. The simulation results demonstrate that the evolution morphology of SMSP melt exhibits perfect dynamic scaling with varying arm numbers; the timescale follows a power-law decay with an exponent θ≃1 as the number of arms increases. The structural constraints on AMSP melts cause the domain growth rate to decrease as the number of one type of arms increases while their length remains fixed. This increase in the number of arms for AMSP corresponds to increased off-criticality. The saturation length in AMSP follows a power-law increase with an exponent λ≃2/3 as off-criticality decreases. Additionally, macrophase separation kinetics in SMSP/AMSP blends show a transition from viscous (ϕ∼1) to inertial (ϕ∼2/3) hydrodynamic growth regimes at late times; this exhibits the same dynamical universality class as linear polymer blends, with slight deviations at early stages.

Structural Rheology in the Development and Study of Complex Polymer Materials

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology-a valuable tool for the development and study of novel materials. This work summarizes the author's structural-rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties.

Aqueous RAFT Dispersion Polymerization Mediated by an ω,ω-Macromolecular Chain Transfer Monomer: An Efficient Approach for Amphiphilic Branched Block Copolymers and the Assemblies

Herein, an ω,ω-macromolecular chain transfer monomer (macro-CTM) containing a RAFT (reversible addition-fragmentation chain transfer) group and a methacryloyl group was synthesized and used to mediate photoinitiated RAFT dispersion polymerization of hydroxypropyl methacrylate (HPMA) in water. The macro-CTM undergoes a self-condensing vinyl polymerization (SCVP) mechanism under RAFT dispersion polymerization conditions, leading to the formation of amphiphilic branched block copolymers and the assemblies. Compared with RAFT solution polymerization, it was found that the SCVP process was promoted under RAFT dispersion polymerization conditions. Morphologies of branched block copolymer assemblies could be controlled by varying the monomer concentration and the [HPMA]/[macro-CTM] ratio. The branched block copolymer vesicles could be used as seeds for seeded RAFT emulsion polymerization, and framboidal vesicles were successfully obtained. Finally, degrees of branching of branched block copolymers could be further controlled by using a binary mixture of the macro-CTM and a linear macro-RAFT agent or a small molecule CTM. We believe that this study not only provides a versatile strategy for the preparation of branched block copolymer assemblies but also offers important insights into polymer synthesis via heterogeneous RAFT polymerization.

Straightforward synthesis of complex polymeric architectures with ultra-high chain density

Synthesis of complex polymeric architectures (CPAs) via reversible-deactivation radical polymerization (RDRP) currently relies on the rather inefficient attachment of monofunctional initiation/transfer sites onto CPA precursors. This drawback seriously limits the overall functionality of the resulting (macro)initiators and, consequently, also the total number of installable polymeric chains, which represents a significant bottleneck in the design of new polymeric materials. Here, we show that the (macro)initiator functionality can be substantially amplified by using trichloroacetyl isocyanate as a highly efficient vehicle for the rapid and clean introduction of trichloroacetyl groups (TAGs) into diverse precursors. Through extensive screening of polymerization conditions and comprehensive NMR and triple-detection SEC studies, we demonstrate that TAGs function as universal trifunctional initiators of copper-mediated RDRP of different monomer classes, affording low-dispersity polymers in a wide molecular weight range. We thus unlock access to a whole new group of ultra-high chain density CPAs previously inaccessible via simple RDRP protocols. We highlight new opportunities in CPA synthesis through numerous examples, including the de novo one-pot synthesis of a novel "star-on-star" CPA, the preparation of β-cyclodextrin-based 45-arm star polymers, and facile grafting from otherwise problematic cellulose substrates both in solution and from surface, obtaining effortlessly ultra-dense, ultra-high-molecular weight bottle-brush copolymers and thick spatially-controlled polymeric coatings, respectively.

Efficient Synthesis of μ-A(BC)C Miktoarm Star Polymer Assemblies via Aqueous Photoinitiated Polymerization-Induced Self-Assembly

In this study, green light-activated photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization of glycerol methacrylate was performed using an ω,ω-heterodifunctional macro-RAFT agent. Because of the different RAFT controllability of two RAFT groups toward methacrylic monomers, only one RAFT group was activated under green light irradiation, leading to the formation of a diblock copolymer macro-RAFT agent with one RAFT group located at the chain end and the other RAFT group located between two blocks. The obtained diblock copolymer macro-RAFT agent was then used to mediate aqueous photoinitiated RAFT dispersion polymerization of diacetone acrylamide (DAAM), which formed μ-A(BC)C miktoarm star polymer assemblies with a diverse set of morphologies. Comparing with the ABC triblock copolymer, it was found that the architecture of the μ-A(BC)C miktoarm star polymer facilitated the formation of higher-order morphologies. Kinetic studies indicated that the aqueous photoinitiated RAFT dispersion polymerization exhibited ultrafast polymerization behavior, with quantitative monomer conversion being achieved within 5 min. Size exclusion chromatography analysis confirmed that good RAFT control was maintained during the polymerization. A morphological phase diagram for μ-A(BC)C miktoarm star polymer assemblies was constructed by varying the monomer concentration and the [DAAM]/[Macro-RAFT] ratio. We expect that this study not only develops an approach for the preparation of miktoarm star polymer assemblies but also provides mechanistic insights into the polymerization-induced self-assembly of nonlinear polymers.

Topological Programmability of Isomerizable Polymers

Topology isomerizable networks (TINs) can be programmed into numerous polymers exhibiting unique and spatially defined (thermo-) mechanical properties. However, capturing the dynamics in topological transformations and revealing the intrinsic mechanisms of mechanical property modulation at the microscopic level is a significant challenge. Here, we use a combination of coarse-grained molecular dynamics simulations and reaction kinetic theory to reveal the impact of dynamic bond exchange reactions on the topology of branched chains. We find that, the grafted units follow a geometric distribution with a converged uniformity, which depends solely on the average grafted units of branched chains. Furthermore, we demonstrate that the topological structure can lead to spontaneous modulation of mechanical properties. The theoretical framework provides a research paradigm for studying the topology and mechanical properties of TINs.

pH-induced morphological transition of aggregates formed by miktoarm star polymers in dilute solution: a mesoscopic simulation study

The self-assembly of miktoarm star polymers μ-A i (B(D)) j C k in a neutral solution and the pH-responsive behaviors of vesicles and spherical micelles in an acidic solution have been investigated by DPD simulation. The results show that the self-assembled morphologies can be regulated by the lengths of pH-responsive arm B and hydrophilic arm C, leading to the formation of vesicles, discoidal micelles, and spherical micelles in a neutral solution. The dynamic evolution pathways of vesicles and spherical micelles are categorized into three stages: nucleation, coalescence, and growth. Subsequently, the pH-responsive behaviors of vesicles and spherical micelles have been explored by tuning the protonation degree of pH-responsive arm B. The vesicles evolves from nanodisks to nanosheets, then to nanoribbons, as the protonation degree increases, corresponding to a decrease in pH value, while the spherical micelles undergoes a transition into worm-like micelles, nanosheets, and nanoribbons. Notably, the electrostatic interaction leads the counterions to form a regular hexagonal pattern in nanosheets, while an alternative distribution of charged beads has been observed in nanoribbons. Furthermore, the role of the electrostatic interaction in the morphological transition has been elucidated through the analysis of the distribution of positive and negative charges, as well as the electrostatic potential for associates.

Synthesis of star-shaped poly(lactide)s, poly(valerolactone)s and poly(caprolactone)s via ROP catalyzed by N-donor tin(ii) cations and comparison of their wetting properties with linear analogues

In this study, we report the use of N-coordinated tin(ii) cations [L1→Sn(H2O)][OTf]2·THF (1) and [L1→SnCl][SnCl3] (2) (L1 = 1,2-(C5H4N-2-CH = N)2CH2CH2) as efficient ROP catalysts, which, in combination with benzyl alcohol, afford well-defined linear poly(ε-caprolactone) (PCL) and poly(δ-valerolactones) (PVL) via an activated monomer mechanism (AMM). Thanks to the versatility of complexes 1 and 2 as catalysts, star-shaped PCL, PVL and PLA were also prepared using three-, four-, five- and six-functional alcohols. The number of arms was determined by SEC-MALS-Visco analysis. Spin-coated thin layers of linear and selected six-armed polymers were further studied in terms of their wettability to water. Attention was focused on the influence of the composition and structure of the polymers. Finally, to increase the hydrophobic properties of the studied polymers, stannaboroxines L2(Ph)Sn[(OB-(C6H4-4-CF3))2O] and L2(Ph)Sn[(OB-(C6H4-3,5-CF3)2)2O] (L2 = C6H3-2,6-(Me2NCH2)2) were applied.

Thermal Solution Depolymerization of RAFT Telechelic Polymers

Thermal solution depolymerization is a promising low-temperature chemical recycling strategy enabling high monomer recovery from polymers made by controlled radical polymerization. However, current methodologies predominantly focus on the depolymerization of monofunctional polymers, limiting the material scope and depolymerization pathways. Herein, we report the depolymerization of telechelic polymers synthesized by RAFT polymerization. Notably, we observed a significant decrease in the molecular weight (Mn) of the polymers during monomer recovery, which contrasts the minimal Mn shift observed during the depolymerization of monofunctional polymers. Introducing Z groups at the center or both ends of the polymer resulted in distinct kinetic profiles, indicating partial depolymerization of the bifunctional polymers, as supported by mathematical modeling. Remarkably, telechelic polymers featuring R-terminal groups showed up to 68% improvement in overall depolymerization conversion compared to their monofunctional analogues, highlighting the potential of these materials in chemical recycling and the circular economy.

Semi-crystalline polymers with supramolecular synergistic interactions: from mechanical toughening to dynamic smart materials

Semi-crystalline polymers (SCPs) with anisotropic amorphous and crystalline domains as the basic skeleton are ubiquitous from natural products to synthetic polymers. The combination of chemically incompatible hard and soft phases contributes to unique thermal and mechanical properties. The further introduction of supramolecular interactions as noncovalently interacting crystal phases and soft dynamic crosslinking sites can synergize with covalent polymer chains, thereby enabling effective energy dissipation and dynamic rearrangement in hierarchical superstructures. Therefore, this review will focus on the design principles of SCPs by discussing supramolecular construction strategies and state-of-the-art functional applications from mechanical toughening to sophisticated functions such as dynamic adaptivity, shape memory, ion transport, etc. Current challenges and further opportunities are discussed to provide an overview of possible future directions and potential material applications.

From Facile One-Pot Synthesis of Semi-Degradable Amphiphilic Miktoarm Polymers to Unique Degradation Properties

We report a one-pot synthesis of well-defined A5B and A8B miktoarm star-shaped polymers where N,N-dimethylaminoethyl methacrylate (DMAEMA) and various cyclic esters such as ε-caprolactone (ε-CL), lactide (LA) and glycolide (GA) were used for the synthesis. Miktopolymers were obtained by simultaneously carrying out atom transfer radical polymerization (ATRP) of DMAEMA, ring-opening polymerization (ROP) of cyclic esters, and click reaction between the azide group in gluconamide-based (GLBr5-Az) or lactonamide-based (GLBr8-Az) ATRP initiators and 4-pentyn-1-ol. The relatively low dispersity indices of the obtained miktoarm stars (Đ = 1.2-1.6) indicate that control over the polymerization processes was sustained despite almost complete monomers conversions (83-99%). The presence of salts from phosphate-buffered saline (PBS) in polymer solutions affects the phase transition, increasing cloud point temperatures (TCP) values. The critical aggregation concentration (CAC) values increased with a decreasing number of average molecular weights of the hydrophobic fraction. Hydrolytic degradation studies revealed that the highest reduction of molecular weight was observed for polymers with PCL and PLGCL arm. The influence of the composition on the miktopolymers hydrophilicity was investigated via water contact angle (WCA) measurement. Thermogravimetric analysis (TGA) disclosed that the number of arms and their composition in the miktopolymer affects its weight loss under the influence of temperature.

RGD-tagging of star-shaped PLA-PEG micellar nanoassemblies enhances doxorubicin efficacy against osteosarcoma

We developed cyclic RGD-tagged polymeric micellar nanoassemblies for sustained delivery of Doxorubicin (Dox) endowed with significant cytotoxic effect against MG63, SAOS-2, and U2-OS osteosarcoma cells without compromising the viability of healthy osteoblasts (hFOBs). Targeted polymeric micellar nanoassemblies (RGD-NanoStar@Dox) enabled Dox to reach the nucleus of MG63, SAOS-2, and U2-OS cells causing the same cytotoxic effect as free Dox, unlike untargeted micellar nanoassemblies (NanoStar@Dox) which failed to reach the nucleus and resulted ineffective, demonstrating the crucial role of cyclic RGD peptide in driving cellular uptake and accumulation mechanisms in osteosarcoma cells. Micellar nanoassemblies were obtained by nanoformulation of three-armed star PLA-PEG copolymers properly synthetized with and without decoration with the cyclic-RGDyK peptide (Arg-Gly-Asp-D-Tyr-Lys). The optimal RGD-NanoStar@Dox nanoformulation obtained by nanoprecipitation method (8 % drug loading; 35 % encapsulation efficiency) provided a prolonged and sustained drug release with a rate significantly lower than the free drug under the same experimental conditions. Moreover, the nanosystem preserved Dox from the natural degradation occurring under physiological conditions (i.e., dimerization and consequent precipitation) serving as a slow-release "drug reservoir" ensuring an extended biological activity over the time.

Highly Selective Electrochemical Baeyer-Villiger Oxidation through Oxygen Atom Transfer from Water

The Baeyer-Villiger oxidation of ketones is a crucial oxygen atom transfer (OAT) process used for ester production. Traditionally, Baeyer-Villiger oxidation is accomplished by thermally oxidizing the OAT from stoichiometric peroxides, which are often difficult to handle. Electrochemical methods hold promise for breaking the limitation of using water as the oxygen atom source. Nevertheless, existing demonstrations of electrochemical Baeyer-Villiger oxidation face the challenges of low selectivity. We report in this study a strategy to overcome this challenge. By employing a well-known water oxidation catalyst, Fe2O3, we achieved nearly perfect selectivity for the electrochemical Baeyer-Villiger oxidation of cyclohexanone. Mechanistic studies suggest that it is essential to produce surface hydroperoxo intermediates (M-OOH, where M represents a metal center) that promote the nucleophilic attack on ketone substrates. By confining the reactions to the catalyst surfaces, competing reactions (e.g., dehydrogenation, carboxylic acid cation rearrangements, and hydroxylation) are greatly limited, thereby offering high selectivity. The surface-initiated nature of the reaction is confirmed by kinetic studies and spectroelectrochemical characterizations. This discovery adds nucleophilic oxidation to the toolbox of electrochemical organic synthesis.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Accelerated Sequence Design of Star Block Copolymers: An Unbiased Exploration Strategy via Fusion of Molecular Dynamics Simulations and Machine Learning

Star block copolymers (s-BCPs) have potential applications as novel surfactants or amphiphiles for emulsification, compatibilization, chemical transformations, and separations. s-BCPs have chain architectures where three or more linear diblock copolymer arms comprised of two chemically distinct linear polymers, e.g., solvophobic and solvophilic chains, are covalently joined at one point. The chemical composition of each of the subunit polymer chains comprising the arms, their molecular weights, and the number of arms can be varied to tailor the surface and interfacial activity of these architecturally unique molecules. This makes identification of the optimal s-BCP design nontrivial as the total number of plausible s-BCP architectures is experimentally or computationally intractable. In this work, we use molecular dynamics (MD) simulations coupled with a reinforcement learning-based Monte Carlo tree search (MCTS) to identify s-BCP designs that minimize the interfacial tension between polar and nonpolar solvents. We first validate the MCTS approach for the design of small- and medium-sized s-BCPs and then use it to efficiently identify sequences of copolymer blocks for large-sized s-BCPs. The structural origins of interfacial tension in these systems are also identified by using the configurations obtained from MD simulations. Chemical insights into the arrangement of copolymer blocks that promote lower interfacial tension were mined using machine learning (ML) techniques. Overall, this work provides an efficient approach to solve design problems via fusion of simulations and ML and provides important groundwork for future experimental investigation of s-BCPs for various applications.

Advances in microbial exoenzymes bioengineering for improvement of bioplastics degradation

Plastic pollution has become a major global concern, posing numerous challenges for the environment and wildlife. Most conventional ways of plastics degradation are inefficient and cause great damage to ecosystems. The development of biodegradable plastics offers a promising solution for waste management. These plastics are designed to break down under various conditions, opening up new possibilities to mitigate the negative impact of traditional plastics. Microbes, including bacteria and fungi, play a crucial role in the degradation of bioplastics by producing and secreting extracellular enzymes, such as cutinase, lipases, and proteases. However, these microbial enzymes are sensitive to extreme environmental conditions, such as temperature and acidity, affecting their functions and stability. To address these challenges, scientists have employed protein engineering and immobilization techniques to enhance enzyme stability and predict protein structures. Strategies such as improving enzyme and substrate interaction, increasing enzyme thermostability, reinforcing the bonding between the active site of the enzyme and substrate, and refining enzyme activity are being utilized to boost enzyme immobilization and functionality. Recently, bioengineering through gene cloning and expression in potential microorganisms, has revolutionized the biodegradation of bioplastics. This review aimed to discuss the most recent protein engineering strategies for modifying bioplastic-degrading enzymes in terms of stability and functionality, including enzyme thermostability enhancement, reinforcing the substrate binding to the enzyme active site, refining with other enzymes, and improvement of enzyme surface and substrate action. Additionally, discovered bioplastic-degrading exoenzymes by metagenomics techniques were emphasized.

Effect of Star Topology Versus Linear Polymers on Antifungal Activity and Mammalian Cell Toxicity

The global increase in invasive fungal infections and the emergence of drug-resistant strains demand the urgent development of novel antifungal drugs. In this context, synthetic polymers with diverse compositions, mimicking natural antimicrobial peptides, have shown promising potential for combating fungal infections. This study investigates how altering polymer end-groups and topology from linear to branched star-like structures affects their efficacy against Candida spp., including clinical isolates. Additionally, the polymers' biocompatibility is accessed with murine embryonic fibroblasts and red blood cells in vitro. Notably, a low-molecular weight star polymer outperforms both its linear polymeric counterparts and amphotericin B (AmpB) in terms of an improved therapeutic index and reduced haemolytic activity, despite a higher minimum inhibitory concentration against Candida albicans (C. albicans) SC5314 (16-32 µg mL-1 vs 1 µg mL-1 for AmpB). These findings demonstrate the potential of synthetic polymers with diverse topologies as promising candidates for antifungal applications.

Supramolecular Synthesis of Star Polymers

Supramolecular polymers, in which monomers are assembled via intermolecular interactions, have been extensively studied. The fusion of supramolecular polymers with conventional polymers has attracted the attention of many researchers. In this review article, the recent progress in the construction of supramolecular star polymers, including regular star polymers and miktoarm star polymers, is discussed. The initial sections briefly provide an overview of the conventional classification and synthesis methods for star polymers. Coordination-driven self-assembly was investigated for the supramolecular synthesis of star polymers. Star polymers with multiple polymer chains radiating from metal-organic polyhedra (MOPs) have also been described. Particular focus has been placed on the synthesis of star polymers featuring supramolecular cores formed through hydrogen-bonding-directed self-assembly. After describing the synthesis of star polymers based on host-guest complexes, the construction of miktoarm star polymers based on the molecular recognition of coordination capsules is detailed.

Using RAFT Polymerization Methodologies to Create Branched and Nanogel-Type Copolymers

This review aims to highlight the most recent advances in the field of the synthesis of branched copolymers and nanogels using reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerization is a reversible deactivation radical polymerization technique (RDRP) that has gained tremendous attention due to its versatility, compatibility with a plethora of functional monomers, and mild polymerization conditions. These parameters lead to final polymers with good control over the molar mass and narrow molar mass distributions. Branched polymers can be defined as the incorporation of secondary polymer chains to a primary backbone, resulting in a wide range of complex macromolecular architectures, like star-shaped, graft, and hyperbranched polymers and nanogels. These subcategories will be discussed in detail in this review in terms of synthesis routes and properties, mainly in solutions.

Star-PCL shape memory polymer (SMP) scaffolds with tunable transition temperatures for enhanced utility

Thermoresponsive shape memory polymers (SMPs) prepared from UV-curable poly(ε-caprolactone) (PCL) macromers have the potential to create self-fitting bone scaffolds, self-expanding vaginal stents, and other shape-shifting devices. To ensure tissue safety during deployment, the shape actuation temperature (i.e., the melt transition temperature or Tm of PCL) must be reduced from ∼55 °C that is observed for scaffolds prepared from linear-PCL-DA (Mn ∼ 10 kg mol-1). Moreover, increasing the rate of biodegradation would be advantageous, facilitating bone tissue healing and potentially eliminating the need for stent retrieval. Herein, a series of six UV-curable PCL macromers were prepared with linear or 4-arm star architectures and with Mns of 10, 7.5, and 5 kg mol-1, and subsequently fabricated into six porous scaffold compositions (10k, 7.5k, 5k, 10k★, 7.5k★, and 5k★) via solvent casting particulate leaching (SCPL). Scaffolds produced from star-PCL-tetraacrylate (star-PCL-TA) macromers produced pronounced reductions in Tm with decreased Mnversus those formed with the corresponding linear-PCL-diacrylate (linear-PCL-DA) macromers. Scaffolds were produced with the desired reduced Tm profiles: 37 °C < Tm < 55 °C (self-fitting bone scaffold), and Tm ≤ 37 °C (self-expanding stent). As macromer Mn decreased, crosslink density increased while % crystallinity decreased, particularly for scaffolds prepared from star-PCL-TA macromers. While shape memory behavior was retained and radial expansion pressure increased, this imparted a reduction in modulus but with an increase in the rate of degradation.

Well-defined star (co)polypeptides via a fast, efficient, and metal-free strategy

Polypeptides, especially star polypeptides, as a unique kind of biological macromolecules have broad applications in biomedical fields such as drug release, gene delivery, tissue engineering, and regenerative medicines due to their close structural similarity to naturally occurring peptides and proteins, biocompatibility, and amino acid functionality. However, the synthesis of star polypeptide mainly relies on the conventional primary amine-initiated ring-opening polymerization (ROP) of N-carboxyanhydrides (NCA) and suffers from low polymerization activity and limited controllability. This study proposes a fast, efficient and metal-free strategy to access star (co)polypeptides by combining the Michael reaction between acrylates and secondary aminoalcohols with the hydrogen-bonding organocatalytic ROP of NCA. This approach enables the preparation of a library of star (co)polypeptides with predesigned molecular weights, narrow molecular weight distributions, tunable arm number, and arm compositions. Importantly, this method exhibits high activity and selectivity at room temperature, making it both practical and versatile in synthesis applications.

Fast and Scalable Synthetic Route to Densely Grafted, Branched Polystyrenes and Polydienes via Anionic Polymerization Utilizing P2VP as Branching Point

Defined, branched polymer architectures with low dispersity and architectural purity are of great interest to polymer science but are challenging to synthesize. Besides star and comb, especially the pom-pom topology is of interest as it is the simplest topology with exactly two branching points. Most synthetic approaches to a pom-pom topology reported a lack of full control and variability over one of the three topological parameters, the backbone or arm molecular weight and arm number. A new, elegant, fast, and scalable synthetic route without the need for post-polymerization modification (PPM) or purification steps during the synthesis to a pom-pom and a broad variety of topologies made from styrene and dienes is reported, with potential application to barbwire, bottlebrush, miktoarm star, Janus type polymers, or multi-graft copolymers. The key is to inset short poly(2-vinyl-pyridine) blocks (<2 mol% in the branched product) into the backbone as branching points. Carb anions can react at the C6 carbon of the pyridine ring, grafting the arms onto the backbone. Since the synthetic route to polystyrene pom-poms has only two steps and is free of PPM or purification, large amounts of up to 300 g of defined pom-pom structures can be synthesized in one batch.