Nanostructured functional materials prepared by atom transfer radical polymerization

Organic nanoparticles with tunable size and rigidity by hyperbranching and cross-linking using microemulsion ATRP

Unlike inorganic nanoparticles, organic nanoparticles (oNPs) offer the advantage of "interior tailorability," thereby enabling the controlled variation of physicochemical characteristics and functionalities, for example, by incorporation of diverse functional small molecules. In this study, a unique inimer-based microemulsion approach is presented to realize oNPs with enhanced control of chemical and mechanical properties by deliberate variation of the degree of hyperbranching or cross-linking. The use of anionic cosurfactants led to oNPs with superior uniformity. Benefitting from the high initiator concentration from inimer and preserved chain-end functionality during atom transfer radical polymerization (ATRP), the capability of oNPs as a multifunctional macroinitiator for the subsequent surface-initiated ATRP was demonstrated. This facilitated the synthesis of densely tethered poly(methyl methacrylate) brush oNPs. Detailed analysis revealed that exceptionally high grafting densities (~1 nm-2) were attributable to multilayer surface grafting from oNPs due to the hyperbranched macromolecular architecture. The ability to control functional attributes along with elastic properties renders this "bottom-up" synthetic strategy of macroinitiator-type oNPs a unique platform for realizing functional materials with a broad spectrum of applications.

Highly efficient dual photoredox/copper catalyzed atom transfer radical polymerization achieved through mechanism-driven photocatalyst design

Atom transfer radical polymerization (ATRP) with dual photoredox/copper catalysis combines the advantages of photo-ATRP and photoredox-mediated ATRP, utilizing visible light and ensuring broad monomer scope and solvent compatibility while minimizing side reactions. Despite its popularity, challenges include high photocatalyst (PC) loadings (10 to 1000 ppm), requiring additional purification and increasing costs. In this study, we discover a PC that functions at the sub-ppm level for ATRP through mechanism-driven PC design. Through studying polymerization mechanisms, we find that the efficient polymerizations are driven by PCs whose ground state oxidation potential-responsible for PC regeneration-play a more important role than their excited state reducing power, responsible for initiation. This is verified by screening PCs with varying redox potentials and triplet excited state generation capabilities. Based on these findings, we identify a highly efficient PC, 4DCDP-IPN, featuring moderate excited state reducing power and a maximized ground state oxidation potential. Employing this PC at 50 ppb, we synthesize poly(methyl methacrylate) with high conversion, narrow molecular weight distribution, and high chain-end fidelity. This system exhibits oxygen tolerance and supports large-scale reactions under ambient conditions. Our findings, driven by the systematic PC design, offer meaningful insights for controlled radical polymerizations and metallaphotoredox-mediated syntheses beyond ATRP.

Robust Miniemulsion PhotoATRP Driven by Red and Near-Infrared Light

Photoinduced polymerization techniques have gathered significant attention due to their mild conditions, spatiotemporal control, and simple setup. In addition to homogeneous media, efforts have been made to implement photopolymerization in emulsions as a practical and greener process. However, previous photoinduced reversible deactivation radical polymerization (RDRP) in heterogeneous media has relied on short-wavelength lights, which have limited penetration depth, resulting in slow polymerization and relatively poor control. In this study, we demonstrate the first example of a highly efficient photoinduced miniemulsion ATRP in the open air driven by red or near-infrared (NIR) light. This was facilitated by the utilization of a water-soluble photocatalyst, methylene blue (MB+). Irradiation by red/NIR light allowed for efficient excitation of MB+ and subsequent photoreduction of the ATRP deactivator in the presence of water-soluble electron donors to initiate and mediate the polymerization process. The NIR light-driven miniemulsion photoATRP provided a successful synthesis of polymers with low dispersity (1.09 ≤ Đ ≤ 1.29) and quantitative conversion within an hour. This study further explored the impact of light penetration on polymerization kinetics in reactors of varying sizes and a large-scale reaction (250 mL), highlighting the advantages of longer-wavelength light, particularly NIR light, for large-scale polymerization in dispersed media owing to its superior penetration. This work opens new avenues for robust emulsion photopolymerization techniques, offering a greener and more practical approach with improved control and efficiency.

Modern Trends in Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered.

Copper Nanodrugs by Atom Transfer Radical Polymerization

In this study, some copper catalysts used for atom transfer radical polymerization (ATRP) were explored as efficient anti-tumor agents. The aqueous solution of copper-containing nanoparticles with uniform spheric morphology was in situ prepared through a copper-catalyzed activator generated by electron transfer (AGET) ATRP in water. Nanoparticles were then directly injected into tumor-bearing mice for antitumor chemotherapy. The copper nanodrugs had prolonged blood circulation time and enhanced accumulation at tumor sites, thus showing potent antitumor activity. This work provides a novel strategy for precise and large-scale preparation of copper nanodrugs with high antitumor activity.

Selective and Controlled Grafting from PVDF-Based Materials by Oxygen-Tolerant Green-Light-Mediated ATRP

Poly(vinylidene fluoride) (PVDF) shows excellent chemical and thermal resistance and displays high dielectric strength and unique piezoelectricity, which are enabling for applications in membranes, electric insulators, sensors, or power generators. However, its low polarity and lack of functional groups limit wider applications. While inert, PVDF has been modified by grafting polymer chains by atom transfer radical polymerization (ATRP), albeit via an unclear mechanism, given the strong C-F bonds. Herein, we applied eosin Y and green-light-mediated ATRP to modify PVDF-based materials. The method gave nearly quantitative (meth)acrylate monomer conversions within 2 h without deoxygenation and without the formation of unattached homopolymers, as confirmed by control experiments and DOSY NMR measurements. The gamma distribution model that accounts for broadly dispersed polymers in DOSY experiments was essential and serves as a powerful tool for the analysis of PVDF. The NMR analysis of poly(methyl acrylate) graft chain-ends on PVDF-CTFE (statistical copolymer with chlorotrifluoroethylene) was carried out successfully for the first time and showed up to 23 grafts per PVDF-CTFE chain. The grafting density was tunable depending on the solvent composition and light intensity during the grafting. The initiation proceeded either from the C-Cl sites of PVDF-CTFE or via unsaturations in the PVDF backbones. The dehydrofluorinated PVDF was 20 times more active than saturated PVDF during the grafting. The method was successfully applied to modify PVDF, PVDF-HFP, and Viton A401C. The obtained PVDF-CTFE-g-PnBMA materials were investigated in more detail. They featured slightly lower crystallinity than PVDF-CTFE (12-18 vs 24.3%) and had greatly improved mechanical performance: Young's moduli of up to 488 MPa, ductility of 316%, and toughness of 46 × 106 J/m3.

Synthesis of Mechanically Robust Very High Molecular Weight Polyisoprene Particle Brushes by Atom Transfer Radical Polymerization

Linear polyisoprene (PI) and SiO2-g-PI particle brushes were synthesized by both conventional and activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP). The morphology and solution state study on the particle brushes by transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the successful grafting of PI ligands on the silica surface. The presence of nanoparticle clusters suggests low grafting density (associated with the limited initiation efficiency of ARGET for PI). Nevertheless, particle brushes with very high molecular weights, Mn > 300,000, were prepared, which significantly improved the dispersion of silica nanoparticles and also contributed to excellent mechanical performance. The reinforcing effects of SiO2 nanofillers and very high molecular weight PI ligands were investigated by dynamic mechanical analysis (DMA) as well as computational simulation for the cured linear PI homopolymer/SiO2-g-PI particle brush bulk films.

Growth kinetics and morphology characterization of binary polymeric fluid under random photo-illumination

We present a comprehensive study using dissipative particle dynamics simulations to investigate phase separation kinetics (PSK) in three-dimensional (3d) polymeric fluids under random photo-illumination. We consider two scenarios: polymer blends with active radicals at one end of each immiscible chain and block copolymer (BCP) melts with photosensitive bonds linking incompatible blocks. The phase separation (PS) is induced by temperature quench of the initial homogeneously mixed system. Simultaneously, the system experiences random photo-illumination, simulated by two concurrent random events: (a) the recombination of active radicals in polymer blends and (b) the breaking of photosensitive bonds in BCP chains. Variations in the bond-breaking probability, Pb, mimic the change in light intensity. The length scale follows power law growth, R(t) ∼ tϕ, where ϕ represents the growth exponent. Increasing Pb results in a gradual transition in growth kinetics from micro-PS to macro-PS, accompanied by corresponding transition probabilities for both systems. Micro-PSK dominates the evolution process at low Pb values. The scaling functions exhibit data overlap for most scaled distances, indicating the statistical self-similarity of evolving patterns. Our study enhances the understanding of PSK in polymeric fluids, revealing the impact of photosensitive bonds and active radicals. Furthermore, it suggests the potential for designing novel polymeric materials with desired properties.

Modification of nanocellulose via atom transfer radical polymerization and its reinforcing effect in waterborne UV-curable resin

Cellulose nanocrystals (CNCs) are green reinforcing materials, and their potential has been evaluated in the preparation of waterborne UV-curable resin composites with high-performance. Herein, we present a novel and scalable approach for preparing surface-modified CNCs with acrylic-based polymers to strengthen the compatibility and interaction between CNCs and UV-curable resins. Using tert-butyl acrylate as the monomer, the nanocellulose grafted copolymer CNC-g-PtBA was successfully synthesized via atom transfer radical polymerization (ATRP) in the presence of a macromolecular initiator. Then, the CNC-g-PtBA is blended into the acrylic resin as a nanofiller to prepare the UV-curable nanocomposite. The results indicated that the contact angle of the CNCs increased from 38.7° to approximately 74.8°, and their thermal stability was significantly improved after graft modification. This contributed to the effective alleviation of the agglomeration phenomenon of nanocomposites due to the high hydrophilicity of pure CNCs. Notably, not only was the UV curing efficiency of the nanocomposites greatly increased but the mechanical properties were also further enhanced. Specifically, with the addition of 0.5 wt% CNC-g-PtBA, the curing time of the nanocomposite was shortened from >30 mins down to approximately 6 mins, and the bending strength was increased from 10 MPa for the original resin and 5 MPa for the addition of pure CNCs to 14.3 MPa, and the bending modulus was also greatly increased (up to approximately 730 MPa). Compared to pure CNCs, they are compatible with the resin, exhibiting high mechanical strength and flexibility, and have virtually no effect on the light transmission of the nanocomposites. Additionally, dielectric analysis (DEA) was used to monitor the dielectric constant and conductivity of the UV-curable nanocomposites in real time to further characterize their curing kinetics. The permittivity of these nanocomposites increased by 125 % compared to pristine resin, which shows potential for applications in high dielectric composites or for improving electrical conductivity. This work provides a feasible method for preparing UV-curable nanocomposites with high curing efficiency and permittivity, realizing a wider application of this high-performance nanocomposite.

Controlled Radical Copolymerization toward Well-Defined Fluoropolymers

In the past 80 years, fluoropolymers have found broad applications in both industrial and academic settings, owing to their unique physicochemical properties. Copolymerizations of fluoroalkene feedstocks present an important avenue to obtain high-performance materials by merging intrinsic attributes of fluorocarbons and great versatility of comonomers. Recently, while massive investigations have disclosed the great potentials of precisely synthesized polymers, researchers have made considerable efforts to approach well-defined fluorinated copolymers. This minireview discusses challenges in controlled radical copolymerizations (CRCPs) of fluoroalkenes and provides a concise perspective on recent progress in CRCPs of fluoroalkenes (e.g., tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropene, perfluoroalkyl vinyl ethers) with non-fluorinated vinyl comonomers, which have enabled on-demand preparations of various main-chain fluoropolymers with predefined molar masses, low dispersities, as well as regulable chemical compositions and sequences. The synthetic advantages of CRCPs will promote controlled and facile access to customized fluoropolymers for high-tech applications such as batteries, coatings and so on.

Biomass RNA for the Controlled Synthesis of Degradable Networks by Radical Polymerization

Nucleic acids extracted from biomass have emerged as sustainable and environmentally friendly building blocks for the fabrication of multifunctional materials. Until recently, the fabrication of biomass nucleic acid-based structures has been facilitated through simple crosslinking of biomass nucleic acids, which limits the possibility of material properties engineering. This study presents an approach to convert biomass RNA into an acrylic crosslinker through acyl imidazole chemistry. The number of acrylic moieties on RNA was engineered by varying the acylation conditions. The resulting RNA crosslinker can undergo radical copolymerization with various acrylic monomers, thereby offering a versatile route for creating materials with tunable properties (e.g., stiffness and hydrophobic characteristics). Further, reversible-deactivation radical polymerization methods, such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT), were also explored as additional approaches to engineer the hydrogel properties. The study also demonstrated the metallization of the biomass RNA-based material, thereby offering potential applications in enhancing electrical conductivity. Overall, this research expands the opportunities in biomass-based biomaterial fabrication, which allows tailored properties for diverse applications.

Thermoresponsive Smart Copolymer Coatings Based on P(NIPAM-co-HEMA) and P(OEGMA-co-HEMA) Brushes for Regenerative Medicine

The fabrication of multifunctional, thermoresponsive platforms for regenerative medicine based on polymers that can be easily functionalized is one of the most important challenges in modern biomaterials science. In this study, we utilized atom transfer radical polymerization (ATRP) to produce two series of novel smart copolymer brush coatings. These coatings were based on copolymerizing 2-hydroxyethyl methacrylate (HEMA) with either oligo(ethylene glycol) methyl ether methacrylate (OEGMA) or N-isopropylacrylamide (NIPAM). The chemical compositions of the resulting brush coatings, namely, poly(oligo(ethylene glycol) methyl ether methacrylate-co-2-hydroxyethyl methacrylate) (P(OEGMA-co-HEMA)) and poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (P(NIPAM-co-HEMA)), were predicted using reactive ratios of the monomers. These predictions were then verified using time-of-flight-secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The thermoresponsiveness of the coatings was examined through water contact angle (CA) measurements at different temperatures, revealing a transition driven by lower critical solution temperature (LCST) or upper critical solution temperature (UCST) or a vanishing transition. The type of transition observed depended on the chemical composition of the coatings. Furthermore, it was demonstrated that the transition temperature of the coatings could be easily adjusted by modifying their composition. The topography of the coatings was characterized using atomic force microscopy (AFM). To assess the biocompatibility of the coatings, dermal fibroblast cultures were employed, and the results indicated that none of the coatings exhibited cytotoxicity. However, the shape and arrangement of the cells were significantly influenced by the chemical structure of the coating. Additionally, the viability of the cells was correlated with the wettability and roughness of the coatings, which determined the initial adhesion of the cells. Lastly, the temperature-induced changes in the properties of the fabricated copolymer coatings effectively controlled cell morphology, adhesion, and spontaneous detachment in a noninvasive, enzyme-free manner that was confirmed using optical microscopy.

Radical chemistry in polymer science: an overview and recent advances

Radical chemistry is one of the most important methods used in modern polymer science and industry. Over the past century, new knowledge on radical chemistry has both promoted and been generated from the emergence of polymer synthesis and modification techniques. In this review, we discuss radical chemistry in polymer science from four interconnected aspects. We begin with radical polymerization, the most employed technique for industrial production of polymeric materials, and other polymer synthesis involving a radical process. Post-polymerization modification, including polymer crosslinking and polymer surface modification, is the key process that introduces functionality and practicality to polymeric materials. Radical depolymerization, an efficient approach to destroy polymers, finds applications in two distinct fields, semiconductor industry and environmental protection. Polymer chemistry has largely diverged from organic chemistry with the fine division of modern science but polymer chemists constantly acquire new inspirations from organic chemists. Dialogues on radical chemistry between the two communities will deepen the understanding of the two fields and benefit the humanity.

Tailored PVDF Graft Copolymers via ATRP as High-Performance NCM811 Cathode Binders

High-nickel layered oxides, e.g., LiNi0.8Co0.1Mn0.1O2 (NCM811), are promising candidates for cathode materials in high-energy-density lithium-ion batteries (LIBs). Complementing the notable developments of modification of active materials, this study focused on the polymer binder materials, and a new synthetic route was developed to engineer PVDF binders by covalently grafting copolymers from poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) with multiple functionalities using atom transfer radical polymerization (ATRP). The grafted random copolymer binder provided excellent flexibility (319% elongation), adhesion strength (50 times higher than PVDF), transition metal chelation capability, and efficient ionic conductivity pathways. The NCM811 half-cells using the designed binders exhibited a remarkable rate capability of 143.4 mA h g-1 at 4C and cycling stability with 70.1% capacity retention after 230 cycles at 0.5 C, which is much higher than the 52.3% capacity retention of nonmodified PVDF. The well-retained structure of NCM811 with the designed binder was systematically studied and confirmed by post-mortem analysis.

Copolymer Brush Particle Hybrid Materials with "Recall-and-Repair" Capability

The effect of sequence structure on the self-healing and shape-memory properties of copolymer-tethered brush particle films was investigated and compared to linear copolymer analogs. Poly(n-butyl acrylate-co-methyl methacrylate), P(BA-co-MMA), and linear and brush analogs with controlled gradient and statistical sequence were synthesized by atom transfer radical polymerization (ATRP). The effect of sequence on self-healing in BA/MMA copolymer brush particle hybrids followed similar trends as for linear analogs. Most rapid restoration of mechanical properties was found for statistical copolymer sequence; an increase of the high Tg (MMA) component provided a path to raise the material's modulus while retaining self-heal ability. Creep testing revealed profound differences between linear and brush systems. While linear copolymers featured substantial viscous deformation when exposed to constant stress in the linear regime, brush analogs displayed minimal permanent deformation and featured shape restoration. The reduction of flow was interpreted to be a consequence of slow cooperative relaxation due to the complex microstructure of brush particle hybrids in which long-range motions are constrained through entanglements and slow-diffusing particle cores. The rubbery-like response imparts BA/MMA copolymer brush material systems concurrent "shape-memory" and "self-heal" capability. This ability to "recall-and-repair" could find application in the design of functional hybrid materials, for example, for soft robotics.

Ketyl Radical Anion Mediated Radical Polymerization and Anionic Ring-Opening Polymerization to Give Polymers with Low Molecular Weight Distribution

The development of novel polymerization capable of yielding polymers with low molecular weight distribution (Đ) is essential and significant in polymer chemistry, where monofunctional initiator contains only one initiation site in these polymerizations generally. Here, ketyl radical anion species is introduced to develop a novel Ketyl Mediated Polymerization (KMP), which enables radical polymerization at carbon radical site and anionic ring-opening polymerization at oxygen anion site, respectively. Meanwhile, polymerization and corresponding organic synthesis generally couldn't be performed simultaneously in one pot. Through KMP, organic synthesis and polymerization are achieved in one pot, where small molecules (cyclopentane derivates) and polymers with low Đ are successfully prepared under mild condition simultaneously. At the initiation step, both organic synthesis and polymerization are initiated by single electron transfer reaction with ketyl radical anion formation. Cyclopentane derivates are synthesized through 3-3 coupling reaction and cyclization. Polystyrene and polycaprolactone with low Đ and a full monomer conversion are prepared by KMP via radical polymerization and anionic ring-opening polymerization, respectively. This work therefore enables both organic synthesis and two different polymerizations from same initiation system, which saves time, labour, resource and energy and expands the reaction mode and method libraries of organic chemistry and polymer chemistry.

Comparison of Mechano- and PhotoATRP with ZnO Nanocrystals

Zinc oxide (ZnO) was previously reported as an excellent cocatalyst for mechanically controlled atom transfer radical polymerization (mechanoATRP), but its photocatalytic properties in photoinduced ATRP (photoATRP) have been much less explored. Herein, well-defined ZnO nanocrystals were prepared via microwave-assisted synthesis and applied as a heterogeneous cocatalyst in mechano- and photoATRP. Both techniques yielded polymers with outstanding control over the molecular weight, but ZnO-cocatalyzed photoATRP was much faster than analogous mechanoATRP (conversion of 91% in 1 h vs 54% in 5 h). The kinetics of photoATRP was tuned by loadings of ZnO nanocrystals. PhotoATRP with ZnO did not require any excess of ligand versus Cu, in contrast to mechanoATRP, requiring an excess of ligand, acting as a reducing agent. ZnO-cocatalyzed photoATRP proceeded controllably without prior deoxygenation, since ZnO was involved in a cascade of reactions, leading to the rapid elimination of oxygen. The versatility and robustness of the technique were demonstrated for various (meth)acrylate monomers with good temporal control and preservation of end-group functionality, illustrated by the formation of tailored block copolymers.

Highly Sensitive Detection of Bacteria by Binder-Coupled Multifunctional Polymeric Dyes

Infectious diseases caused by pathogens are a health burden, but traditional pathogen identification methods are complex and time-consuming. In this work, we have developed well-defined, multifunctional copolymers with rhodamine B dye synthesized by atom transfer radical polymerization (ATRP) using fully oxygen-tolerant photoredox/copper dual catalysis. ATRP enabled the efficient synthesis of copolymers with multiple fluorescent dyes from a biotin-functionalized initiator. Biotinylated dye copolymers were conjugated to antibody (Ab) or cell-wall binding domain (CBD), resulting in a highly fluorescent polymeric dye-binder complex. We showed that the unique combination of multifunctional polymeric dyes and strain-specific Ab or CBD exhibited both enhanced fluorescence and target selectivity for bioimaging of Staphylococcus aureus by flow cytometry and confocal microscopy. The ATRP-derived polymeric dyes have the potential as biosensors for the detection of target DNA, protein, or bacteria, as well as bioimaging.

Biocompatible Polymer-Grafted TiO2 Nanoparticle Sonosensitizers Prepared Using Phosphonic Acid-Functionalized RAFT Agent

Sonodynamic therapy is widely used in clinical studies including cancer therapy. The development of sonosensitizers is important for enhancing the generation of reactive oxygen species (ROS) under sonication. Herein, we have developed poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-modified TiO₂ nanoparticles as new biocompatible sonosensitizers with high colloidal stability under physiological conditions. To fabricate biocompatible sonosensitizers, a grafting-to approach was adopted with phosphonic-acid-functionalized PMPC, which was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) using a newly designed water-soluble RAFT agent possessing a phosphonic acid group. The phosphonic acid group can conjugate with the OH groups on the TiO₂ nanoparticles. We have clarified that the phosphonic acid end group is more crucial for creating colloidally stable PMPC-modified TiO₂ nanoparticles under physiological conditions than carboxylic-acid-functionalized PMPC-modified ones. Furthermore, the enhanced generation of singlet oxygen (¹O₂), an ROS, in the presence of PMPC-modified TiO₂ nanoparticles was confirmed using a ¹O₂-reactive fluorescent probe. We believe that the PMPC-modified TiO₂ nanoparticles prepared herein have potential utility as novel biocompatible sonosensitizers for cancer therapy.

Supramolecular Polymerization of Polymeric Nanorods Mediated by Block Copolymers

Introducing a second component is an effective way to manipulate polymerization behavior. However, this phenomenon has rarely been observed in colloidal systems, such as polymeric nanoparticles. Here, we report the supramolecular polymerization of polymeric nanorods mediated by block copolymers. Experimental observations and simulation results illustrate that block copolymers surround the polymeric nanorods and mainly concentrate around the two ends, leaving the hydrophobic side regions exposed. These polymeric nanorods connect in a side-by-side manner through hydrophobic interactions to form bundles. As polymerization progresses, the block copolymers gradually deposit onto the bundles and finally assemble into helical nanopatterns on the outermost surface, which terminates the polymerization. It is anticipated that this work could offer inspiration for a general strategy of controllable supramolecular polymerization.

Ferritin-Enhanced Direct MicroRNA Detection via Controlled Radical Polymerization

Accurate quantitative detection of tracing nucleic acids remains a great challenge in cancer genetic testing. It is crucial to propose a low-cost and highly sensitive direct gene detection method for cancer prevention and treatment. Herein, this work reports an ultrasensitive biosensor via a ferritin-enhanced atom-transfer radical polymerization (Ft-ATRP) process. Intriguingly, microRNA-21, an early marker of lung cancer, can be detected without being transcribed in advance by an innovative signal amplification strategy using ferritin-mediated aggregation of hydrophilic nitroxide radical monomers as an electrochemical biosensor. The sensor uses peptide nucleic acid probes modified on a gold electrode to accurately bind the target lung cancer marker in the sample, and then ferritin, which is naturally present in human blood, induces Ft-ATRP on the electrode surface under mild conditions. Many of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (MATMP) monomers with electrochemical signals are combined into polymeric chains to be modified on target assays. The limit of detection (LOD) of microRNA-21 is as low as 6.03 fM, and the detection concentration ranges from 0.01 to 100 pM (R² = 0.994). The RNA biosensor can realize great performance analysis of complicated samples in simple operation, in addition, the detection process used by the catalyst, polymers containing electrochemical signals, and the electrolyte solution all have good water solubility. The superior performance of the RNA biosensor demonstrates its potential to screen and identify lung cancer in target patients.

Polymer- and lipid-based gene delivery technology for CAR T cell therapy

Chimeric antigen receptor T cell (CAR T cell) therapy is a revolutionary approach approved by the FDA and EMA to treat B cell malignancies and multiple myeloma. The production of these T cells has been done through viral vectors, which come with safety concerns, high cost and production challenges, and more recently also through electroporation, which can be extremely cytotoxic. In this context, nanosystems can constitute an alternative to overcome the challenges associated with current methods, resulting in a safe and cost-effective platform. However, the barriers associated with T cells transfection show that the design and engineering of novel approaches in this field are highly imperative. Here, we present an overview from CAR constitution to transfection technologies used in T cells, highlighting the lipid- and polymer-based nanoparticles as a potential delivery platform. Specifically, we provide examples, strengths and weaknesses of nanosystem formulations, and advances in nanoparticle design to improve transfection of T cells. This review will guide the researchers in the design and development of novel nanosystems for next-generation CAR T therapeutics.

Tuning Single-Polymer Growth via Hydrogen Bonding in Conformational Entanglements

Synthetic polymers have widespread applications in daily life and advanced materials applications. Making polymers efficiently and controllably is highly desired, for which modulating intramolecular and intermolecular interactions have been an effective approach. Recent real-time single-polymer growth studies uncovered nonequilibrium conformational entanglements that form stochastically under living polymerization conditions and which appear to plausibly play key roles in controlling the polymerization kinetics and dispersion. Here, using magnetic tweezers measurements, we study the real-time polymerization dynamics of single polynorbornene-based polymers in which we systematically tune the hydrogen-bonding interactions by titrating the OH content in the monomers and the formed polymers during ring opening metathesis polymerization. Using norbornenes with and without a hydroxyl group and a nonreactive monomer analogue, we show that intrachain and intermolecular hydrogen bonding compete, and both alter the microscopic properties of the nonequilibrium entanglements, leading to surprising multiphasic dependences of polymerization dynamics on the polymer's OH content. We further formulate a simple model to rationalize quantitatively the observed multiphasic behaviors by considering the different scaling relations of intrachain and intermolecular hydrogen bonding on the OH content. These results provide insights into the interconnected roles of intra-/intermolecular interactions, polymer chain conformations, and free monomers in solution in affecting polymerization kinetics and dispersion, and point to new opportunities in manipulating polymerization reactions.

Sulfoxide-Containing Polyacrylamides Prepared by PICAR ATRP for Biohybrid Materials

Water-soluble and biocompatible polymers are of interest in biomedicine as the search for alternatives to PEG-based materials becomes more important. In this work, the synthesis of a new sulfoxide-containing monomer, 2-(methylsulfinyl)ethyl acrylamide (MSEAM), is reported. Well-defined polymers were prepared by photoinduced initiators for continuous activator regeneration atom transfer radical polymerization (PICAR ATRP). The polymerizations were performed in water under biologically relevant conditions in a small volume without degassing the reaction mixture. DNA-PMSEAM and protein-PMSEAM hybrids were also synthesized. The lower critical solution temperature (LCST) of PMSEAM was estimated to be approximately 170 °C by extrapolating the LCST for a series of copolymers with variable content of N-isopropylacrylamide. The cytotoxicity studies showed excellent biocompatibility of PMSEAM, even at concentrations up to 2.5 mg/mL. Furthermore, the MSEAM monomer exhibited relatively lower toxicity than similar (meth)acrylate-based monomers at comparable concentrations.

Star-Shaped ROMP Polymers Coated with Oligothiophenes That Exhibit Unique Emission

A series of oligo(thiophene)-modified "soluble" star-shaped ring-opening metathesis polymerization (ROMP) polymers were prepared by sequential living ROMP of norbornene and a cross-linking agent using a molybdenum-alkylidene catalyst, followed by Wittig-type coupling for termination with oligo(thiophene) carboxaldehydes. The resultant star-shaped ROMP polymers displayed unique emission properties affected by the core size and arm repeat units as well as the kind of oligothiophene coated. The effects of the thiophene groups on photophysical properties of star-shaped/linear polymers were studied via time-resolved fluorescence spectroscopy. Fluorescence lifetimes were determined in THF as 400, 640, 730, and 820 ps for Star 3TPh, Linear 3TPh, Star 4T, and Linear 4T, respectively. A significant enhancement of the nonradiative rate constants k _nr in the star-shaped polymers results in relatively lower fluorescence quantum yields and shorter fluorescence lifetimes compared to the corresponding linear polymers.

Supramolecular Helical Miktoarm Star Polymers

We report a hydrogen-bonded supramolecular miktoarm star polymer containing three distinct helical arms. Our design involves two helical poly(methacrylamide) arms connected by a barbituric acid (Ba) at the center, prepared through the reversible addition-fragmentation chain-transfer polymerization with a bifunctional agent. Together with a telechelic helical poly(isocyanide) end-functionalized with a Hamilton Wedge (HW) that is complementary to Ba, the two components assemble into an AB₂-type star copolymer. The assembly is driven by the hydrogen bonding between HW and Ba, which is quantified by ¹H NMR titration and isothermal titration calorimetry. Gel-permeation chromatography provides evidence for the formation of the desired miktoarm star architecture. This strategy of site-specific functionalization on helical polymers provides a modular approach to preparing nonlinear supramolecular ensembles with topologically diverse building blocks.

Transformer-Induced Metamorphosis of Polymeric Nanoparticle Shape at Room Temperature

Controlled polymerizations have enabled the production of nanostructured materials with different shapes, each exhibiting distinct properties. Despite the importance of shape, current morphological transformation strategies are limited in polymer scope, alter the chemical structure, require high temperatures, and are fairly tedious. Herein we present a rapid and versatile morphological transformation strategy that operates at room temperature and does not impair the chemical structure of the constituent polymers. By simply adding a molecular transformer to an aqueous dispersion of polymeric nanoparticles, a rapid evolution to the next higher‐order morphology was observed, yielding a range of morphologies from a single starting material. Significantly, this approach can be applied to nanoparticles produced by disparate block copolymers obtained by various synthetic techniques including emulsion polymerization, polymerization‐induced self‐assembly and traditional solution self‐assembly.

Ionic strength dependent forces between end-grafted Poly(sulfobetaine) films and mica

The molecular surface properties of zwitterionic polymer coatings are central to their ultra-low fouling properties and effectiveness as steric stabilizers in concentrated salt solutions. Here, Surface Force Apparatus measurements quantified the molecular forces between end-grafted poly(sulfobetaine) methacrylate thin films and mica, as a function of the chain grafting density and ionic strength. These results demonstrate that, at the ionic strengths considered, end-grafted poly(sulfobetaine) films can be described by models for polymers in good solvent. Parameters determined from data fits to the Milner-Witten-Cates or Dolan and Edwards models for dense or dilute chains, respectively, varied with ionic strength, in ways that reflect poly(sulfobetaine) swelling and the increased excluded volume strength of chain segments. These force measurements provide new insight into how polymer coverage and salt cooperate to regulate repulsive poly(sulfobetaine) steric barriers. These findings have implications for the design of grafted poly(sulfobetaine) as colloidal stabilizers or nonfouling surface coatings.

The challenges of controlling polymer synthesis at the molecular and macromolecular level

In this Perspective, we outline advances and challenges in controlling the structure of polymers at various size regimes in the context of structural features such as molecular weight distribution, end groups, architecture, composition and sequence.

Open-air green-light-driven ATRP enabled by dual photoredox/copper catalysis

Photoinduced atom transfer radical polymerization (photo-ATRP) has risen to the forefront of modern polymer chemistry as a powerful tool giving access to well-defined materials with complex architecture. However, most photo-ATRP systems can only generate radicals under biocidal UV light and are oxygen-sensitive, hindering their practical use in the synthesis of polymer biohybrids. Herein, inspired by the photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization, we demonstrate a dual photoredox/copper catalysis that allows open-air ATRP under green light irradiation. Eosin Y was used as an organic photoredox catalyst (PC) in combination with a copper complex (X–Cu^II/L). The role of PC was to trigger and drive the polymerization, while X–Cu^II/L acted as a deactivator, providing a well-controlled polymerization. The excited PC was oxidatively quenched by X–Cu^II/L, generating Cu^I/L activator and PC˙⁺. The ATRP ligand (L) used in excess then reduced the PC˙⁺, closing the photocatalytic cycle. The continuous reduction of X–Cu^II/L back to Cu^I/L by excited PC provided high oxygen tolerance. As a result, a well-controlled and rapid ATRP could proceed even in an open vessel despite continuous oxygen diffusion. This method allowed the synthesis of polymers with narrow molecular weight distributions and controlled molecular weights using Cu catalyst and PC at ppm levels in both aqueous and organic media. A detailed comparison of photo-ATRP with PET-RAFT polymerization revealed the superiority of dual photoredox/copper catalysis under biologically relevant conditions. The kinetic studies and fluorescence measurements indicated that in the absence of the X–Cu^II/L complex, green light irradiation caused faster photobleaching of eosin Y, leading to inhibition of PET-RAFT polymerization. Importantly, PET-RAFT polymerizations showed significantly higher dispersity values (1.14 ≤ Đ ≤ 4.01) in contrast to photo-ATRP (1.15 ≤ Đ ≤ 1.22) under identical conditions.

Fully oxygen-tolerant photoinduced atom transfer radical polymerization (photo-ATRP) allowed the synthesis of well-defined polymers using a Cu catalyst and eosin Y at ppm levels in both aqueous and organic media.