Star Polymers

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.

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.

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.

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.

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.

Efficient gene delivery by multifunctional star poly (β-amino ester)s into difficult-to-transfect macrophages for M1 polarization

Gene delivery to macrophages holds great promise for cancer immunotherapy. However, traditional gene delivery methods exhibit low transfection efficiency in macrophages. The star-shaped topological structure of polymers is known to encapsulate genes inside their cores, thereby facilitating sustained release of the genetic material. Herein, combining the structural advantages of star polymers and the transfection advantages of poly (β-amino ester)s (PAEs), we developed a novel linear oligomer grafting-onto strategy to synthesize a library of multi-terminal star structured PAEs (SPAEs), and evaluated their gene delivery efficiency in various tissue cells. The transfection with human hepatocellular carcinoma cells (HepG2, HCC-LM3 cells and MHCC-97H cells), rat normal liver cells (BRL-3 A cells), human ovarian cancer cells (A2780 cells), African green monkey kidney cells (Vero cells), human cervical cancer cells (HeLa cells), human chondrosarcoma cells (SW1353 cells), and difficult-to-transfect human epidermal keratinocytes (HaCaT cells) and normal human fibroblast cells (NHF cells) showed that SPAEs exhibited superior transfection profile. The GFP transfection efficiency of top-performing SPAEs in HeLa cells (96.1%) was 2.1-fold, and 3.2-fold higher compared to jetPEI and Lipo3000, respectively, indicating that the star-shaped topological structure can significantly enhance the transfection efficiency of PAEs. More importantly, the top-performing SPAEs could efficiently deliver Nod2 DNA to difficult-to-transfect RAW264.7 macrophages, with a high transfection efficiency of 33.9%, which could promote macrophage M1 polarization and enhanced CD8+ T cell response in co-incubation experiments. This work advances gene therapy by targeting difficult-to-transfect macrophages and remodeling the tumor immune microenvironment.

Phase Behavior of Charged Star Block Copolymers at Fluids Interface

The phase behavior of block copolymers (BCPs) at the water-oil interface is influenced by the segmental interaction parameter ( χ ${\chi }$ ) and chain architecture. We synthesized a series of star block copolymers (s-BCPs) having polystyrene (PS) as core and poly(2-vinylpyridine) (P2VP) as corona. The interaction parameters of block-block ( χ ${\chi }$ PS-P2VP ) and block-solvent ( χ ${\chi }$ P2VP-solvent ) were varied by adjusting the pH of the aqueous solution. Lowering pH increased the fraction of quaternized-P2VP (Q-P2VP) with enhanced hydrophilicity. By transferring the equilibrated interfacial assemblies, morphologies ranging from bicontinuous films at pH of 7 and 3.1 to nanoporous and nanotubular structure at pH of 0.65 were observed. The nanoporous films formed hexagonally packed pores in s-BCP matrix, while nanotubes comprised Q-P2VP as corona and PS as core. Control over pore size, d-spacing between pores, and nanotube diameters was achieved by varying polymer concentration, molecular weight, volume fraction and arm number of s-BCPs. Large-scale nanoporous films were obtained by freeze-drying emulsions. Remarkably, the morphologies of linear BCPs were inverted, forming hexagonal-packed rigid spherical micelles with Q-P2VP as core and PS as corona in multilayer. This work provides insights of phase behaviors of BCP at fluids interface and offer a facile approach to prepare nanoporous film with well-controlled pore structure.

Enhancing Targeted Photodynamic Therapy: Star-Shaped Glycopolymeric Photosensitizers for Improved Selectivity and Efficacy

Targeted photodynamic therapy (PDT) offers advantages over nontargeted approaches, including improved selectivity, efficacy, and reduced side effects. This study developed star-shaped glycopolymeric photosensitizers using porphyrin-based initiators via ATRP. Incorporating a porphyrin core gave the polymers fluorescence and ROS generation, while adding fructose improved solubility and targeting capabilities. The photosensitizers had high light absorption, singlet oxygen production, specificity, low dark toxicity, and biocompatibility. The glycopolymers with longer sugar arms and higher density showed better uptake on MCF-7 and MDA-MB-468 cells compared to HeLa cells, indicating enhanced targeting capabilities. Inhibition of endocytosis confirmed the importance of the GLUT5 receptor. The resulting polymers exhibited good cytocompatibility under dark conditions and satisfactory PDT under light irradiation. Interestingly, the polymers containing fructose have a GLUT5-dependent elimination effect on the MCF-7 and MDA-MB-468 cells. The intracellular ROS production followed a similar pattern, indicating that the fructose polymer exhibits specific targeting toward cells with GLUT5 receptors.

Universal scaling of the osmotic pressure for dense, quasi-two-dimensionally confined polymer melts reveals transitions between fractal dimensions

A scaling law for the osmotic pressure of quasi-two-dimensional polymer melts as a function of concentration is obtained, which shows fractal characteristics. Structural properties such as the chains' contour length and their inner-monomer pair distribution function display fractal scaling properties as well. These predictions are confirmed with mesoscale numerical simulations. The chains are swollen and highly entangled, yet Flory's exponent is always ν = 1/2. The melt can be considered a fluid of "blobs" whose size becomes renormalized in terms of the contour's length while the fractal dimension df increases monotonically between 5/4 and 2, as the monomer concentration is increased. The semidilute scaling of the pressure is recovered when df = 1. Our results agree with recent experiments and with numerical reports on quasi-2d melts. This work provides a new paradigm to study and interpret thermodynamic and structural data in low-dimensional polymer melts, namely as fractal macromolecular objects.

Janus bottlebrush compatibilizers

Bottlebrush random copolymers (BRCPs), consisting of a random distribution of two homopolymer chains along a backbone, can segregate to the interface between two immiscible homopolymers. BRCPs undergo a reconfiguration, where each block segregates to one of the homopolymer phases, adopting a Janus-type structure, reducing the interfacial tension and promoting adhesion between the two homopolymers, thereby serving as a Janus bottlebrush copolymer (JBCP) compatibilizer. We synthesized a series of JBCPs by copolymerizing deuterated or hydrogenated polystyrene (DPS/PS) and poly(tert-butyl acrylate) (PtBA) macromonomers using ruthenium benzylidene-initiated ring-opening metathesis polymerization (ROMP). Subsequent acid-catalyzed hydrolysis converted the PtBA brushes to poly(acrylic acid) (PAA). The JBCPs were then placed at the interface between DPS/PS homopolymers and poly(2-vinyl pyridine) (P2VP) homopolymers, where the degree of polymerization of the backbone (NBB) and the grafting density (GD) of the JBCPs were varied. Neutron reflectivity (NR) was used to determine the interfacial width and segmental density distributions (including PS homopolymer, PS block, PAA block and P2VP homopolymer) across the polymer-polymer interface. Our findings indicate that the star-like JBCP with NBB = 6 produces the largest interfacial broadening. Increasing NBB to 100 (rod-like shape) and 250 (worm-like shape) reduced the interfacial broadening due to a decrease in the interactions between blocks and homopolymers by stretching of blocks. Decreasing the GD from 100% to 80% at NBB = 100 caused an increase the interfacial width, yet further decreasing the GD to 50% and 20% reduced the interfacial width, as 80% of GD may efficiently increase the flexibility of blocks and promote interactions between homopolymers, while maintaining relatively high number of blocks attached to one molecule. The interfacial conformation of JBCPs was further translated into compatibilization efficiency. Thin film morphology studies showed that only the lower NBB values (NBB = 6 and NBB = 24) and the 80% GD of NBB = 100 had bicontinuous morphologies, due to a sufficient binding energy that arrested phase separation, supported by mechanical testing using asymmetric double cantilever beam (ADCB) tests. These provide fundamental insights into the assembly behavior of JBCPs compatibilizers at homopolymer interfaces, opening strategies for the design of new BCP compatibilizers.

Structural Element of Vitamin U-Mimicking Antibacterial Polypeptide with Ultrahigh Selectivity for Effectively Treating MRSA Infections

Antimicrobial peptides (AMPs) exhibit mighty antibacterial properties without inducing drug resistance. Achieving much higher selectivity of AMPs towards bacteria and normal cells has always been a continuous goal to be pursued. Herein, a series of sulfonium-based polypeptides with different degrees of branching and polymerization were synthesized by mimicking the structure of vitamin U. The polypeptide, G2 -PM-1H+ , shows both potent antibacterial activity and the highest selectivity index of 16000 among the reported AMPs or peptoids (e.g., the known index of 9600 for recorded peptoid in "Angew. Chem. Int. Ed., 2020, 59, 6412."), which can be attributed to the high positive charge density of sulfonium and the regulation of hydrophobic chains in the structure. The antibacterial mechanisms of G2 -PM-1H+ are primarily ascribed to the interaction with the membrane, production of reactive oxygen species (ROS), and disfunction of ribosomes. Meanwhile, altering the degree of alkylation leads to selective antibacteria against either gram-positive or gram-negative bacteria in a mixed-bacteria model. Additionally, both in vitro and in vivo experiments demonstrated that G2 -PM-1H+ exhibited superior efficacy against methicillin-resistant Staphylococcus aureus (MRSA) compared to vancomycin. Together, these results show that G2 -PM-1H+ possesses high biocompatibility and is a potential pharmaceutical candidate in combating bacteria significantly threatening human health.

Polymeric Electrolytes for Solid-state Lithium Ion Batteries: Structure Design, Electrochemical Properties and Cell Performances

Solid-state electrolytes are key to achieving high energy density, safety, and stability for lithium-ion batteries. In this Review, core indicators of solid polymer electrolytes are discussed in detail including ionic conductivity, interface compatibility, mechanical integrity, and cycling stability. Besides, we also summarize how above properties can be improved by design strategies of functional monomers, groups, and assembly of batteries. Structures and properties of polymers are investigated here to provide a basis for all-solid-state electrolyte design strategies of multi-component polymers. In addition, adjustment strategies of quasi-solid-state polymer electrolytes such as adding functional additives and carrying out structural design are also investigated, aiming at solving problems caused by simply adding liquids or small molecular plasticizer. We hope that fresh and established researchers can achieve a general perspective of solid polymer electrolytes via this Review and spur more extensive interests for exploration of high-performance lithium-ion batteries.

Capillary filling of star polymer melts in nanopores

The topology of a polymer profoundly influences its behavior. However, its effect on imbibition dynamics remains poorly understood. In the present work, capillary filling (during imbibition and following full imbibition) of star polymer melts was investigated by molecular dynamics simulations with a coarse-grained model. The reversal of imbibition dynamics observed for linear-chain systems was also present for star polymers. Star polymers with short arms penetrate slower than the prediction of the Lucas-Washburn equation, while systems with long arms penetrate faster. The radius of gyration increases during confined flow, indicating the orientation and disentanglement of arms. In addition, the higher the functionality of the star polymer, the more entanglement points are retained. Besides, a stiff region near the core segments of the stars is observed, which increases in size with functionality. The proportion of different configurations of the arms (e.g., loops, trains, tails) changes dramatically with the arm length and degree of confinement but is only influenced by the functionality when the arms are short. Following full imbibition, the different decay rates of the self-correlation function of the core-to-end vector illustrate that arms take a longer time to reach the equilibrium state as the functionality, arm length, and degree of confinement increase, in agreement with recent experimental findings. Furthermore, the star topology induces a stronger effect of adsorption and friction, which becomes more pronounced with increasing functionality.

One-Pot Synthesis, Circularly Polarized Luminescence, and Controlled Self-Assembly of Janus-Type Miktoarm Star Copolymers

With the aim of broadening the scope of Janus-type polymers with new functionalities, Janus-type miktoarm star copolymers comprising helical poly(phenyl isocyanide) (PPI) and a vinyl polymer were designed and synthesized via a combination of Pd(II)-initiated isocyanide polymerization and atom transfer radical polymerization (ATRP). A functional β-cyclodextrin bearing 7 Pd(II) complexes at one side and 14 bromine groups at the other side ((Pd(II))7-CD-(Br)14) was prepared and used as an initiator for the one-pot polymerization of phenyl isocyanide and the ATRP of vinyl monomers in a living and controlled manner. A variety of Janus-type copolymers with different structures and tunable compositions were facilely obtained by using this method. Thus, Janus-type copolymers composed of helical PPIs and tetraphenylethylene-modified vinyl polymers exhibited a significant circularly polarized luminescence performance in both soluble and aggregated states. Meanwhile, Janus-type copolymers containing PPIs and hydrophilic vinyl polymers presented amphiphilicity and self-assembled into diverse morphologies.

Design, preparation, and characterization of lubricating polymer brushes for biomedical applications

The lubrication modification of biomedical devices significantly enhances the functionality of implanted interventional medical devices, thereby providing additional benefits for patients. Polymer brush coating provides a convenient and efficient method for surface modification while ensuring the preservation of the substrate's original properties. The current research has focused on a "trial and error" method to finding polymer brushes with superior lubricity qualities, which is time-consuming and expensive, as obtaining effective and long-lasting lubricity properties for polymer brushes is difficult. This review summarizes recent research advances in the biomedical field in the design, material selection, preparation, and characterization of lubricating and antifouling polymer brushes, which follow the polymer brush development process. This review begins by examining various approaches to polymer brush design, including molecular dynamics simulation and machine learning, from the fundamentals of polymer brush lubrication. Recent advancements in polymer brush design are then synthesized and potential avenues for future research are explored. Emphasis is placed on the burgeoning field of zwitterionic polymer brushes, and highlighting the broad prospects of supramolecular polymer brushes based on host-guest interactions in the field of self-repairing polymer brush applications. The review culminates by providing a summary of methodologies for characterizing the structural and functional attributes of polymer brushes. It is believed that a development approach for polymer brushes based on "design-material selection-preparation-characterization" can be created, easing the challenge of creating polymer brushes with high-performance lubricating qualities and enabling the on-demand creation of coatings. STATEMENT OF SIGNIFICANCE: Biomedical devices have severe lubrication modification needs, and surface lubrication modification by polymer brush coating is currently the most promising means. However, the design and preparation of polymer brushes often involves "iterative testing" to find polymer brushes with excellent lubrication properties, which is both time-consuming and expensive. This review proposes a polymer brush development process based on the "design-material selection-preparation-characterization" strategy and summarizes recent research advances and trends in the design, material selection, preparation, and characterization of polymer brushes. This review will help polymer brush researchers by alleviating the challenges of creating polymer brushes with high-performance lubricity and promises to enable the on-demand construction of polymer brush lubrication coatings.

Brownian dynamics simulations of bottlebrush polymers in dilute solution under simple shear and uniaxial extensional flows

We study the dynamics of bottlebrush polymer molecules in dilute solutions subjected to shear and uniaxial extensional flows using Brownian dynamics simulations with hydrodynamic interaction (HI). Bottlebrush polymers are modeled using a coarse-grained representation, consisting of a set of beads interacting pairwise via a purely repulsive potential and connected by finitely extensible nonlinear springs. We present the results for molecular stretching, stress, and solution viscosity during the startup of flow as well as under steady state as a function of side chain length while keeping the backbone length fixed. In extensional flow, the backbone fractional extension and the first normal stress difference decrease with an increase in side chain length at a fixed Weissenberg number (Wi). Using simulation results both in the presence of and in the absence of HI, we show that this is primarily a consequence of steric interaction resulting from the dense grafting of side chains. In shear flow, we observe a shear-thinning behavior in all cases, although it becomes less pronounced with increasing side chain length. Furthermore, nonmonotonicity in the backbone fractional extension is observed under shear, particularly at high Wi. We contextualize our simulation results for bottlebrush polymers with respect to existing studies in the literature for linear polymers and show that the unique dynamical features characterizing bottlebrush polymers arise on account of their additional molecular thickness due to the presence of densely grafted side chains.

Mechanochemical Oxidative Coupling of Amine to Azo-based Polymers by Hypervalent Iodine Oxidant

Among porous organic polymers (POPs), azo-linked POPs represent a crucial class of materials, making them the focus of numerous catalytic systems proposed for their synthesis. However, the synthetic process is limited to metal-catalyzed, high-temperature, and liquid-phase reactions. In this study, we employ mechanochemical oxidative metal-free systems to encompass various syntheses of azo-based polymers. Drawing inspiration from the "rule of six" principle (six or more carbons on an azide group render the organic compound relatively safe), an azo compound featuring significant steric hindrance is obtained using the hypervalent iodine oxidation strategy. Furthermore, during the polymerization process, steric hindrance is enhanced in monomers to effectively prevent explosions resulting from direct contact between hypervalent iodine oxidants and primary amines. Indeed, this approach provides a facile and innovative solid-phase synthesis method for synthesizing azo-based materials.

Eco-Conscious Approach to Thermoresponsive Star-Comb and Mikto-Arm Polymers via Enzymatically Assisted Atom Transfer Radical Polymerization Followed by Ring-Opening Polymerization

This study explores the synthesis, characterization, and application of a heterofunctional initiator derived from 2-hydroxypropyl cyclodextrin (HP-β-CD), having eight bromoester groups and thirteen hydroxyl groups allowing the synthesis of mikto-arm star-shaped polymers. The bromoesterification of HP-β-CD was achieved using α-bromoisobutyryl bromide as the acylation reagent, modifying the cyclodextrin (CD) molecule as confirmed by electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy analysis, and differential scanning calorimetry (DSC) thermograms. The initiator's effectiveness was further demonstrated by obtaining star-comb and mikto-arm polymers via an enzymatically assisted atom transfer radical polymerization (ATRP) method and subsequent ring-opening polymerization (ROP). The ATR polymerization quality and control depended on the type of monomer and was optimized by the way of introducing the initiator into the reaction mixture. In the case of ATRP, high conversion rates for poly(ethylene oxide) methyl ether methacrylate (OEOMA), with molecular weights (Mn) of 500 g/mol and 300 g/mol, were achieved. The molecular weight distribution of the obtained polymers remained in the range of 1.23-1.75. The obtained star-comb polymers were characterized by different arm lengths. Unreacted hydroxyl groups in the core of exemplary star-comb polymers were utilized in the ROP of ε-caprolactone (CL) to obtain a hydrophilic mikto-arm polymer. Cloud point temperature (TCP) values of the synthesized polymers increased with arm length, indicating the polymers' reduced hydrophobicity and enhanced solvation by water. Atomic force microscopy (AFM) analysis revealed the ability of the star-comb polymers to create fractals. The study elucidates advancements in the synthesis and utilization of hydrophilic sugar-based initiators for enzymatically assisted ATRP in an aqueous solution for obtaining complex star-comb polymers in a controlled manner.

Navigating the Expansive Landscapes of Soft Materials: A User Guide for High-Throughput Workflows

Synthetic polymers are highly customizable with tailored structures and functionality, yet this versatility generates challenges in the design of advanced materials due to the size and complexity of the design space. Thus, exploration and optimization of polymer properties using combinatorial libraries has become increasingly common, which requires careful selection of synthetic strategies, characterization techniques, and rapid processing workflows to obtain fundamental principles from these large data sets. Herein, we provide guidelines for strategic design of macromolecule libraries and workflows to efficiently navigate these high-dimensional design spaces. We describe synthetic methods for multiple library sizes and structures as well as characterization methods to rapidly generate data sets, including tools that can be adapted from biological workflows. We further highlight relevant insights from statistics and machine learning to aid in data featurization, representation, and analysis. This Perspective acts as a "user guide" for researchers interested in leveraging high-throughput screening toward the design of multifunctional polymers and predictive modeling of structure-property relationships in soft materials.

Flexible Poly(vinyl chloride) with Durable Antibiofouling Property via Blending Star-Shaped Amphiphilic Poly(ε-caprolactone)-block-poly(methacryloxyethyl sulfobetaine)

Flexible poly(vinyl chloride) (PVC) plastics have been widely used in medical devices, but the preparation of antibiofouling flexible PVC materials that can maintain their antibiofouling performance when suffering deformation is still a challenge. In this work, we synthesized a series of amphiphilic star-shaped three-arm block copolymers SPCL-b-PSB, consisting of hydrophobic inner blocks poly(ε-caprolactone) (PCL) and hydrophilic outer blocks poly(methacryloxyethyl sulfobetaine) (PSB). Then, flexible PVC films were prepared by blending SPCL-b-PSB with PVC and plasticizer. Benefiting from the specific star-shaped topological structure of SPCL-b-PSB, hydrophilic PSB blocks of the copolymer could efficiently migrate to the surface of the film via annealing treatment, which give the film surface excellent hydrophilicity, while the latch-like entanglements between hydrophobic PCL blocks and PVC give the hydrophilic surface excellent stability. Antibiofouling properties of the blended films were investigated. The optimized blended film could reduce ∼94% of bovine serum albumin adsorption, ∼ 87% of lysozyme adsorption, and ∼89% of platelet adhesion and resist bacterial adhesion effectively. What is more, the blended films could maintain their antibiofouling performance when suffering stretching, rubbing, or bending. More than 86% of bovine serum albumin adsorption could be reduced, even when the film was stretched by 50%. This work provides a new strategy for the preparation of durable antibiofouling flexible plastics.

Four-Arm Polymer-Guided Formation of Curcumin-Loaded Flower-Like Porous Microspheres as Injectable Cell Carriers for Diabetic Wound Healing

Stem cell injection is an effective approach for treating diabetic wounds; however, shear stress during injections can negatively affect their stemness and cell growth. Cell-laden porous microspheres can provide shelter for bone mesenchymal stem cells (BMSC). Herein, curcumin-loaded flower-like porous microspheres (CFPM) are designed by combining phase inversion emulsification with thermally induced phase separation-guided four-arm poly (l-lactic acid) (B-PLLA). Notably, the CFPM shows a well-defined surface topography and inner structure, ensuring a high surface area to enable the incorporation and delivery of a large amount of -BMSC and curcumin. The BMSC-carrying CFPM (BMSC@CFPM) maintains the proliferation, retention, and stemness of -BMSCs, which, in combination with their sustainable curcumin release, facilitates the endogenous production of growth/proangiogenic factors and offers a local anti-inflammatory function. An in vivo bioluminescence assay demonstrates that BMSC@CFPM can significantly increase the retention and survival of BMSC in wound sites. Accordingly, BMSC@CFPM, with no significant systemic toxicity, could significantly accelerate diabetic wound healing by promoting angiogenesis, collagen reconstruction, and M2 macrophage polarization. RNA sequencing further unveils the mechanisms by which BMSC@CFPM promotes diabetic wound healing by increasing -growth factors and enhancing angiogenesis through the JAK/STAT pathway. Overall, BMSC@CFPM represents a potential therapeutic tool for diabetic wound healing.

Fluorescence-readout as a powerful macromolecular characterisation tool

The last few decades have witnessed significant progress in synthetic macromolecular chemistry, which can provide access to diverse macromolecules with varying structural complexities, topology and functionalities, bringing us closer to the aim of controlling soft matter material properties with molecular precision. To reach this goal, the development of advanced analytical techniques, allowing for micro-, molecular level and real-time investigation, is essential. Due to their appealing features, including high sensitivity, large contrast, fast and real-time response, as well as non-invasive characteristics, fluorescence-based techniques have emerged as a powerful tool for macromolecular characterisation to provide detailed information and give new and deep insights beyond those offered by commonly applied analytical methods. Herein, we critically examine how fluorescence phenomena, principles and techniques can be effectively exploited to characterise macromolecules and soft matter materials and to further unravel their constitution, by highlighting representative examples of recent advances across major areas of polymer and materials science, ranging from polymer molecular weight and conversion, architecture, conformation to polymer self-assembly to surfaces, gels and 3D printing. Finally, we discuss the opportunities for fluorescence-readout to further advance the development of macromolecules, leading to the design of polymers and soft matter materials with pre-determined and adaptable properties.

Supramolecular host-guest nanosystems for overcoming cancer drug resistance

Cancer drug resistance has become one of the main challenges for the failure of chemotherapy, greatly limiting the selection and use of anticancer drugs and dashing the hopes of cancer patients. The emergence of supramolecular host-guest nanosystems has brought the field of supramolecular chemistry into the nanoworld, providing a potential solution to this challenge. Compared with conventional chemotherapeutic platforms, supramolecular host-guest nanosystems can reverse cancer drug resistance by increasing drug uptake, reducing drug efflux, activating drugs, and inhibiting DNA repair. Herein, we summarize the research progress of supramolecular host-guest nanosystems for overcoming cancer drug resistance and discuss the future research direction in this field. It is hoped that this review will provide more positive references for overcoming cancer drug resistance and promoting the development of supramolecular host-guest nanosystems.

Exploiting the Monomer-Feeding Mechanism of RAFT Emulsion Polymerization for Polymerization-Induced Self-Assembly of Asymmetric Divinyl Monomers

We exploited the monomer-feeding mechanism of reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization to achieve the successful polymerization-induced self-assembly (PISA) of asymmetric divinyl monomers. Colloidally stable cross-linked block copolymer nanoparticles with various morphologies, such as vesicles, were directly prepared at high solids. Morphologies of the cross-linked block copolymer nanoparticles could be controlled by varying the monomer concentration, degree of polymerization (DP) of the core-forming block, and length of the macro-RAFT agent. X-ray photoelectron spectroscopy (XPS) characterization confirmed the presence of unreacted vinyl groups within the obtained block copolymer nanoparticles, providing a landscape for further functionalization via thiol-ene chemistry. Finally, the obtained block copolymer nanoparticles were employed as additives to tune the mechanical properties of hydrogels. We expect that this study not only offers considerable opportunities for the preparation of well-defined cross-linked block copolymer nanoparticles, but also provides important insights into the controlled polymerization of multivinyl monomers.

Colloidal Polymer-Templated Formation of Inorganic Nanocrystals and their Emerging Applications

Inorganic nanocrystals possess unique physicochemical properties compared to their bulk counterparts. Stabilizing agents are commonly used for the preparation of inorganic nanocrystals with controllable properties. Particularly, colloidal polymers have emerged as general and robust templates for in situ formation and confinement of inorganic nanocrystals. In addition to templating and stabilizing inorganic nanocrystals, colloidal polymers can tailor their physicochemical properties such as size, shape, structure, composition, surface chemistry, and so on. By incorporating functional groups into colloidal polymers, desired functions can be integrated with inorganic nanocrystals, advancing their potential applications. Here, recent advances in the colloidal polymer-templated formation of inorganic nanocrystals are reviewed. Seven types of colloidal polymers, including dendrimer, polymer micelle, stare-like block polymer, bottlebrush polymer, spherical polyelectrolyte brush, microgel, and single-chain nanoparticle, have been extensively applied for the synthesis of inorganic nanocrystals. Different strategies for the development of these colloidal polymer-templated inorganic nanocrystals are summarized. Then, their emerging applications in the fields of catalysis, biomedicine, solar cells, sensing, light-emitting diodes, and lithium-ion batteries are highlighted. Last, the remaining issues and future directions are discussed. This review will stimulate the development and application of colloidal polymer-templated inorganic nanocrystals.

Rationally designed block copolymer-based nanoarchitectures: An emerging paradigm for effective drug delivery

Various polymeric materials have been investigated to produce unique modes of delivery for drug modules to achieve either temporal or spatial control of bioactives delivery. However, after intravenous administration, phagocytic cells quickly remove these nanostructures from the systemic circulation via the reticuloendothelial system (RES). To overcome these concerns, ecofriendly block copolymers are increasingly being investigated as innovative carriers for the delivery of bioactives. In this review, we discuss the design, fabrication techniques, and recent advances in the development of block copolymers and their applications as drug carrier systems to improve the physicochemical and pharmacological attributes of bioactives.

Synthesis of optically active star polymers consisting of helical poly(phenylacetylene) chains by the living polymerization of phenylacetylenes and their chiroptical properties

Star polymers consisting of three helical poly(phenylacetylene) chains with a precisely controlled molecular weight (molar mass dispersity < 1.03) were successfully synthesized by the living polymerization of phenylacetylene derivatives with a Rh-based multicomponent catalyst system comprising trifunctional initiators, which have three phenylboronates centered on a benzene ring, the Rh complex [Rh(nbd)Cl]2, diphenylacetylene, triphenylphosphine, and a base. The analysis of chiroptical properties of the optically active star polymers obtained by the living polymerization of optically active phenylacetylene derivatives revealed that the star polymers exhibited chiral amplification properties owing to their unique topology compared with the corresponding linear polymers.

Catalytic Living ROMP: Synthesis of Degradable Star Polymers

Star polymers have attracted considerable attention over the past few years due to their distinctive physical and chemical attributes that are different from conventional linear polymers. Here, we present a one-pot synthesis of narrowly dispersed and degradable homoarm and miktoarm star polymers exploiting the catalytic living ring-opening metathesis polymerization (ROMP) mechanism. Several complex polymeric architectures (such as A3-, A4-, A6-, A2B-, A3B-, and AB2-type star polymers) were synthesized quite straightforwardly by using appropriate vinyl ether chain transfer agents. SEC, 1H NMR, and DOSY NMR spectroscopy were employed to analyze and characterize all of the synthesized polymers. We believe that this sustainable and environmentally friendly synthesis of star polymers could become an important synthetic tool for polymer engineers working on supramolecular, industrial or biomedical applications.

Emerging Trends in the Chemistry of End-to-End Depolymerization

Over the past couple of decades, polymers that depolymerize end-to-end upon cleavage of their backbone or activation of a terminal functional group, sometimes referred to as "self-immolative" polymers, have been attracting increasing attention. They are of growing interest in the context of enhancing polymer degradability but also in polymer recycling as they allow monomers to be regenerated in a controlled manner under mild conditions. Furthermore, they are highly promising for applications as smart materials due to their ability to provide an amplified response to a specific signal, as a single sensing event is translated into the generation of many small molecules through a cascade of reactions. From a chemistry perspective, end-to-end depolymerization relies on the principles of self-immolative linkers and polymer ceiling temperature (Tc). In this article, we will introduce the key chemical concepts and foundations of the field and then provide our perspective on recent exciting developments. For example, over the past few years, new depolymerizable backbones, including polyacetals, polydisulfides, polyesters, polythioesters, and polyalkenamers, have been developed, while modern approaches to depolymerize conventional backbones such as polymethacrylates have also been introduced. Progress has also been made on the topological evolution of depolymerizable systems, including the introduction of fully depolymerizable block copolymers, hyperbranched polymers, and polymer networks. Furthermore, precision sequence-defined oligomers have been synthesized and studied for data storage and encryption. Finally, our perspectives on future opportunities and challenges in the field will be discussed.

Designing polymers for cartilage uptake: effects of architecture and molar mass

Osteoarthritis (OA) is a progressive disease, involving the progressive breakdown of cartilage, as well as changes to the synovium and bone. There are currently no disease-modifying treatments available clinically. An increasing understanding of the disease pathophysiology is leading to new potential therapeutics, but improved approaches are needed to deliver these drugs, particularly to cartilage tissue, which is avascular and contains a dense matrix of collagens and negatively charged aggrecan proteoglycans. Cationic delivery vehicles have been shown to effectively penetrate cartilage, but these studies have thus far largely focused on proteins or nanoparticles, and the effects of macromolecular architectures have not yet been explored. Described here is the synthesis of a small library of polycations composed of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-(3-aminopropyl)methacrylamide (APMA) with linear, 4-arm, or 8-arm structures and varying degrees of polymerization (DP) by reversible addition fragmentation chain-transfer (RAFT) polymerization. Uptake and retention of the polycations in bovine articular cartilage was assessed. While all polycations penetrated cartilage, uptake and retention generally increased with DP before decreasing for the highest DP. In addition, uptake and retention were higher for the linear polycations compared to the 4-arm and 8-arm polycations. In general, the polycations were well tolerated by bovine chondrocytes, but the highest DP polycations imparted greater cytotoxicity. Overall, this study reveals that linear polymer architectures may be more favorable for binding to the cartilage matrix and that the DP can be tuned to maximize uptake while minimizing cytotoxicity.

Stimuli-responsive rotaxane-branched dendronized polymers with tunable thermal and rheological properties

Aiming at the creation of polymers with attractive dynamic properties, herein, rotaxane-branched dendronized polymers (DPs) with rotaxane-branched dendrons attached onto the polymer chains are proposed. Starting from macromonomers with both rotaxane-branched dendrons and polymerization site, targeted rotaxane-branched DPs are successfully synthesized through ring-opening metathesis polymerization (ROMP). Interestingly, due to the existence of multiple switchable [2]rotaxane branches within the attached dendrons, anion-induced reversible thickness modulation of the resultant rotaxane-branched DPs is achieved, which further lead to tunable thermal and rheological properties, making them attractive platform for the construction of smart polymeric materials.

Multi-Stimuli Responsive Sequence Defined Multi-Arm Star Diblock Copolymers for Controlled Drug Release

Star-shaped polymeric materials provide very high efficiency toward various engineering and biomedical applications. Due to the absence of straightforward and versatile synthetic protocols, the synthesis of sequence-defined star-shaped (co)polymers has remained a major challenge. Here, a facile approach is developed that allows synthesis of a series of unprecedented discrete, multifunctional four-, six-, and eight-arm star-shaped complex macromolecular architectures based on a well-defined triple (thermo/pH/light)-stimuli-responsive poly(N-isopropylacrylamide)-block-poly(methacrylic acid)-umbelliferone (PNIPAM-b-PMAA)n-UMB diblock copolymer, based on temperature responsive PNIPAM segment, pH-responsive PMAA segment, and photoresponsive UMB end groups. Thus, developed star-shaped copolymers self-assemble in water to form spherical nanoaggregates of diameter 90 ± 20 nm, as measured by FESEM. The star-shaped copolymer's response to external stimuli has been assessed against changes in temperature, pH, and light irradiation. The star-shaped copolymer was employed as a nanocarrier for pH responsive release of an anticancer drug, doxorubicin. This study opens up new avenues for efficient star-shaped macromolecular architecture construction for engineering and biomedical applications.

Synthesis of PDMS-μ-PCL Miktoarm Star Copolymers by Combinations (Є) of Styrenics-Assisted Atom Transfer Radical Coupling and Ring-Opening Polymerization and Study of the Self-Assembled Nanostructures

Due to their diverse and unique physical properties, miktoarm star copolymers (μ-SCPs) have garnered significant attention. In our study, we employed α-monobomoisobutyryl-terminated polydimethylsiloxane (PDMS-Br) to carry out styrenics-assisted atom transfer radical coupling (SA ATRC) in the presence of 4-vinylbenzyl alcohol (VBA) at 0 °C. By achieving high coupling efficiency (χc = 0.95), we obtained mid-chain functionalized PDMS-VBAm-PDMS polymers with benzylic alcohols. Interestingly, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis revealed the insertion of only two VBA coupling agents (m = 2). Subsequently, the PDMS-VBA2-PDMS products underwent mid-chain extensions using ε-caprolactone (ε-CL) through ring-opening polymerization (ROP) with an efficient organo-catalyst at 40 °C, resulting in the synthesis of novel (PDMS)2-μ-(PCL)2 μ-SCPs. Eventually, novel (PDMS)2-μ-(PCL)2 μ-SCPs were obtained. The obtained PDMS-μ-PCL μ-SCPs were further subjected to examination of their solid-state self-assembly through small-angle X-ray scattering (SAXS) experiments. Notably, various nanostructures, including lamellae and hexagonally packed cylinders, were observed with a periodic size of approximately 15 nm. As a result, we successfully developed a simple and effective reaction combination (Є) strategy (i.e., SA ATRC-Є-ROP) for the synthesis of well-defined PDMS-μ-PCL μ-SCPs. This approach may open up new possibilities for fabricating nanostructures from siloxane-based materials.