Controlled/living radical polymerization: Features, developments, and perspectives

Surface-grafted macromolecular nanowires with pedant fluorescein chromophores by dense non-aggregated nanoarchitectonics as versatile photoactive platforms

In this paper, we present a facile method of synthesis and modification of poly(glycidyl methacrylate) brushes with 6-aminofluorescein (6AF) molecules. Polymer brushes were obtained using surface-grafted atom transfer radical polymerization (SI-ATRP) and functionalized in the presence of triethylamine (TEA) acting both as a reaction catalyst and an agent preventing aggregation of chromophores. Atomic force microscopy (AFM), FTIR, X-ray photoelectron spectroscopy (XPS) were used to study the structure and formation of obtained photoactive platforms. UV-Vis absorption and emission spectroscopy and confocal microscopy were conducted to investigate photoactivity of chromophores within the macromolecular matrix. Owing to the simplicity of fabrication and good ordering of the chromophore in a thin nanometric layer, the proposed method may open new opportunities for obtaining light sensors, photovoltaic devices, or other light-harvesting systems.

Facile Surface Modification with Croconaine-Functionalized Polymer on Polypropylene for Antifouling and NIR-Light-Mediated Photothermal Sterilization

Biomedical-device-associated infection (BAI) is undoubtedly a major concern and a serious challenge in modern medicine. Therefore, the development of biomedical materials that are capable of resisting or killing bacteria is of great importance. In this work, a croconaine-functionalized polymer with antifouling and near-infrared (NIR) photothermal bactericidal properties was prepared and facilely modified on polypropylene (PP) to combat medical device infections. Croconaine dye is elaborately modified as a "living" initiator, termed CR-4EBiB, for preparing amphiphilic block polymers by atom transfer radical polymerization (ATRP). In the formed polymer coating, the hydrophobic block can strongly adhere to the surface of the PP substrate, whereas the hydrophilic block is located on the outer layer by solvent-induced resistance to bacterial adhesion. Under the irradiation of an NIR laser (808 nm), the croconaine dye in the coating achieved maximum conversion of light to heat to effectively kill E. coli, S. aureus, and methicillin-resistant Staphylococcus aureus (MRSA). This work provides a facile and promising strategy for the development of implantable antibacterial biomedical materials.

Closed-loop recyclable polymers: from monomer and polymer design to the polymerization-depolymerization cycle

The extensive utilization of plastic, as a symbol of modern technological society, has consumed enormous amounts of finite and non-renewable fossil resources and produced huge amounts of plastic wastes in the land or ocean, and thus recycling and reuse of the plastic wastes have great ecological and economic benefits. Closed-loop recyclable polymers with inherent recyclability can be readily depolymerized into monomers with high selectivity and purity and repolymerized into polymers with the same performance. They are deemed to be the next generation of recyclable polymers and have captured great and increasing attention from academia and industry. Herein, we provide an overview of readily closed-loop recyclable polymers based on monomer and polymer design and no-other-reactant-involved reversible ring-opening and addition polymerization reactions. The state-of-the-art of circular polymers is separately summarized and discussed based on different monomers, including lactones, thiolactones, cyclic carbonates, hindered olefins, cycloolefins, thermally labile olefin comonomers, cyclic disulfides, cyclic (dithio) acetals, lactams, Diels-Alder addition monomers, Michael addition monomers, anhydride-secondary amide monomers, and cyclic anhydride-aldehyde monomers, and polymers with activatable end groups. The polymerization and depolymerization mechanisms are clearly disclosed, and the evolution of the monomer structure, the polymerization and depolymerization conditions, the corresponding polymerization yield, molecular weight, performance of the polymers, monomer recovery, and depolymerization equipment are also systematically summarized and discussed. Furthermore, the challenges and future prospects are also highlighted.

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.

Enhancing Cancer Therapy: Boron-Rich Polyboronate Ester Micelles for Synergistic Boron Neutron Capture Therapy and PD-1/PD-L1 Checkpoint Blockade

Malignant cancers, known for their pronounced heterogeneity, pose substantial challenges to monotherapeutic strategies and contribute to the risk of metastasis. Addressing this, our study explores the synergistic potential of combining boron neutron capture therapy (BNCT) with immune checkpoint blockade to enhance cancer treatment efficacy. We synthesized boron-rich block copolymer micelles as a novel boron drug for BNCT. Characterization was conducted using nuclear magnetic resonance, gel-permeation chromatography, transmission electron microscopy, and dynamic light scattering. These micelles, with an optimal size of 91.3 nm and a polydispersity index of 0.18, are suitable for drug delivery applications. In vitro assessments on B16-F10 melanoma cells showed a 13-fold increase in boron uptake with the micelles compared to borophenyl alanine (BPA), the conventional boron drug for BNCT. This resulted in a substantial increase in BNCT efficacy, reducing cell viability to 77% post-irradiation in micelle-treated cells, in contrast to 90% in BPA-treated cells. In vivo, melanoma-bearing mice treated with these micelles exhibited an 8-fold increase in boron accumulation in tumor tissues versus those treated with BPA, leading to prolonged tumor growth delay (5.4 days with micelles versus 3.3 days with BPA). Moreover, combining BNCT with anti-PD-L1 immunotherapy further extended the tumor growth delay to 6.6 days, and enhanced T-cell infiltration and activation at tumor sites, thereby indicating a boosted immune response. This combination demonstrates a promising approach by enhancing cytotoxic T-cell priming and mitigating the immunosuppressive effects of melanoma tumors.

Enhancing Polymer Sustainability: Eco-Conscious Strategies

Polymer sustainability is a pressing concern in today's world driven by the increasing demand for environmentally friendly materials. This review paper provides a comprehensive overview of eco-friendly approaches towards enhancing the sustainability of polymers. It synthesized recent research and developments in various areas such as green polymer synthesis methods, biodegradable polymers, recycling technologies, and emerging sustainable alternatives. The environmental impact of traditional polymer production processes and the importance of adopting greener alternatives were critically examined. The review delved into the advancements in polymer recycling technologies like mechanical, chemical, and biological processes aimed at minimizing plastic waste and promoting a circular economy. The innovative approaches such as upcycling, hybrid methods etc., which offer promising solutions for addressing plastic pollution and achieving long-term sustainability goals were also analyzed. Finally, the paper discussed the challenges and future prospects of eco-friendly approaches for polymer sustainability, emphasizing the need for researchers and concerted efforts from scientists across industries and academia to drive meaningful change towards a more sustainable future.

Biophysical investigation of liposome systems decorated with bioconjugated copolymers in the presence of amantadine

Liposome-based technologies derived from lipids and polymers (e.g., PEGylated liposomes) have been recognized because of their applications in nanomedicine. However, since such systems represent myriad challenges and may promote immune responses, investigation of new biomaterials is mandatory. Here, we report on a biophysical investigation of liposomes decorated with bioconjugated copolymers in the presence (or absence) of amantadine (an antiviral medication). First, copolymers of poly(N,N-dimethylacrylamide-co-fluoresceinacrylate-co-acrylic acid-N-succinimide ester)-block-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM) containing a fluorescence label were biofunctionalized with short peptides that resemble the sequence of the loops 220 and 130 of the binding receptor of the hemagglutinin (HA) protein of the influenza A virus. Then, the bioconjugated copolymers were self-assembled along with liposomes composed of 1,2 dimyristoyl-sn-glycero-3-phosphocholine, sphingomyelin, and cholesterol (MSC). These biohybrid systems, with and without amantadine, were systematically characterized using differential scanning calorimetry (DSC), dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryoTEM). Finally, the systems were tested in an in vitro study to evaluate cytotoxicity and direct immunofluorescence in Madin Darbin Canine Kidney (MDCK) cells. The biohybrid systems displayed long-term stability, thermo-responsiveness, hydrophilic-hydrophobic features, and fluorescence properties and were presumable endowed with cell targeting properties intrinsically integrated into the amino acid sequences of the utilized peptides, which indeed turn them into promising nanodevices for biomedical 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.

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

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

Hydrophilic Poly(meth)acrylates by Controlled Radical Branching Polymerization: Hyperbranching and Fragmentation

Topology significantly impacts polymer properties and applications. Hyperbranched polymers (HBPs) synthesized via atom transfer radical polymerization (ATRP) using inimers typically exhibit broad molecular weight distributions and limited control over branching. Alternatively, copolymerization of inibramers (IB), such as α-chloro/bromo acrylates with vinyl monomers, yields HBPs with precise and uniform branching. Herein, we described the synthesis of hydrophilic HB polyacrylates in water by copolymerizing a water-soluble IB, oligo(ethylene oxide) methyl ether 2-bromoacrylate (OEOBA), with various hydrophilic acrylate comonomers. Visible-light-mediated controlled radical branching polymerization (CRBP) with dual catalysis using eosin Y (EY) and copper complexes resulted in HBPs with various molecular weights (M n = 38 000 to 170 000) and degrees of branching (2%-24%). Furthermore, the optimized conditions enabled the successful application of the OEOBA to synthesize linear-hyperbranched block copolymers and hyperbranched polymer protein hybrids (HB-PPH), demonstrating its potential to advance the synthesis of complex macromolecular architecture under environmentally benign conditions. Copolymerization of hydrophilic methacrylate monomer, oligo(ethylene oxide) methyl ether methacrylate (OEOMA500), and inibramer OEOBA was accompanied by fragmentation via β-carbon C-C bond scission and subsequent growth of polymer chains from the fragments. Furthermore, computational studies investigating the fragmentation depending on the IB and comonomer structure supported the experimental observations. This work expands the toolkit of water-soluble inibramers for CRBP and highlights the critical influence of the inibramer structure on reaction outcomes.

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.

Near-infrared Light-Induced Polymerizations: Mechanisms and Applications

Photopolymerizations have garnered significant attention in polymer science due to their low polymerization temperature, high production efficiency, environmental friendliness, and spatial controllability. Despite these merits, the poor penetration and severe chemical damage from ultraviolet/visible (UV/Vis) light resources pose significant barriers to their success in conventional photopolymerizations. A recent breakthrough involving the utilization of near-infrared (NIR) laser with long wavelength has been exploited for diverse applications. With the combination of a NIR photosensitizer (PS), NIR-induced photopolymerizations have been successfully developed to alleviate the challenges in conventional methods. The enhancement of penetration depth and safety of NIR-induced photopolymerizations can contribute significantly to improving the efficiency of polymerization for production of intricate structures across various scales. In this concept, the typical types of PSs and polymerization mechanisms (PMs) within the NIR-induced photopolymerization systems have been classified in detail. Additionally, the applications of various polymers achieved by NIR-induced photopolymerizations are summarized. Furthermore, research directions and future challenges of this field are also discussed comprehensively.

Does the radical GPRI strongly depend on the population scheme? A comparative study to predict radical attack on unsaturated molecules with the radical general-purpose reactivity indicator

The reactivity of 22 unsaturated molecules undergoing attack by a methyl radical (⋅CH3) have been elucidated using the condensed radical general-purpose reactivity indicator (condensed radical GPRI) appropriate for relatively nucleophilic or electrophilic molecules. Using the appropriate radical GPRI equation for electrophilic attack or nucleophilic radical attack, seven different population schemes were used to assign the most reactive atoms in each of the 22 molecules. The results show that the condensed radical GPRI is sensitive to the population scheme chosen, but less sensitive than the radical Fukui function. Therefore, the reliability of these methods depends on the population scheme. Our investigation indicates that the condensed radical GPRI is most accurate in predicting the dominant products of the methyl radical addition reactions on a variety of unsaturated molecules when the Hirshfeld, Merz-Singh-Kollman, or Voronoi deformation density population schemes are used. Furthermore, for all populations schemes in the majority of instances where the radical Fukui function failed the radical GPRI was able to identify the most reactive atom under certain reactivity conditions.

Bottlebrush Networks: A Primer for Advanced Architectures

Bottlebrush networks (BBNs) are an exciting new class of materials with interesting physical properties derived from their unique architecture. While great strides have been made in our fundamental understanding of bottlebrush polymers and networks, an interdisciplinary approach is necessary for the field to accelerate advancements. This review aims to act as a primer to BBN chemistry and physics for both new and current members of the community. In addition to providing an overview of contemporary BBN synthetic methods, we developed a workflow and desktop application (LengthScale), enabling bottlebrush physics to be more approachable. We conclude by addressing several topical issues and asking a series of pointed questions to stimulate conversation within the community.

Network Polymer Properties Engineered Through Polymer Backbone Dispersity and Structure

Dispersity (Ð or Mw/Mn) is an important parameter in material design and as such can significantly impact the properties of polymers. Here, polymer networks with independent control over the molecular weight and dispersity of the linear chains that form the material are developed. Using a RAFT polymerization approach, a library of polymers with dispersity ranging from 1.2-1.9 for backbone chain-length (DP) 100, and 1.4-3.1 for backbone chain-length 200 were developed and transformed to networks through post-polymerization crosslinking to form disulfide linkers. The tensile, swelling, and adhesive properties were explored, finding that both at DP 100 and DP 200 the swelling ratio, tensile strength, and extensibility were superior at intermediate dispersity (1.3-1.5 for DP 100 and 1.6-2.1 for DP 200) compared to materials with either substantially higher or lower dispersity. Furthermore, adhesive properties for materials with chains of intermediate dispersity at DP 200 revealed enhanced performance compared to the very low or high dispersity chains.

Advances in Organosulfur-Based Polymers for Drug Delivery Systems

Organosulfur-based polymers have unique properties that make them useful for targeted and managed drug delivery, which can improve therapy while reducing side effects. This work aims to provide a brief review of the synthesis strategies, characterization techniques, and packages of organosulfur-based polymers in drug delivery. More importantly, this work discusses the characterization, biocompatibility, controlled release, nanotechnology, and targeted therapeutic aspects of these important structural units. This review provides not only a good comprehension of organosulfur-based polymers but also an insightful discussion of potential future prospectives in research. The discovery of novel organosulfur polymers and innovations is highly expected to be stimulated in order to synthesize polymer prototypes with increased functional accuracy, efficiency, and low cost for many industrial applications.

Radiation polymerization for the preparation of universal coatings: remarkable anti-fogging and frost-resisting performance

Hydrophilic anti-fogging coatings have attracted considerable attention due to their ease of preparation and excellent fog resistance. In this study, a hydrophilic anti-fogging coating based on the random copolymer p(AA-co-SAS) was prepared using acrylic acid (AA) and sodium allylsulfonate (SAS) as monomers through radiation polymerization. The introduction of SAS successfully transformed the random copolymer from a gel state into a film-forming polymer solution. The presence of AA structural units in p(AA-co-SAS) improved the film-forming properties of the polymer solution. Additionally, there was a positive correlation between the proportion of SAS structural units in the random copolymer and the scratch hardness and wetting properties of the coating. After coating polycarbonate (PC) sheets, the surface hydrophilicity was significantly enhanced, with the contact angle of PC-AA10/SAS5 decreasing from 100.1° to 18.8° within 50 seconds. The outstanding wetting properties endowed the coating with exceptional anti-fogging and frost-resisting performance. It exhibited optimal transparency under both testing conditions and demonstrated good stability during cyclic testing. Tape adhesion tests indicated that the adhesion between the coating and PC reached a 5B level. When AA10/SAS5 was applied to PET film, glass, and PMMA goggles, all samples showed excellent anti-fog performance. Even after being naturally placed for one year under ambient conditions, the PMMA goggles still maintained good performance in the anti-fog and frost resistance tests. The remarkable comprehensive properties of the polymer coating based on p(AA-co-SAS) suggest enormous potential applications in industries such as packaging, healthcare, and optical equipment.

A novel method of alkoxyamine homolysis activation via photochemical rearrangement

We proposed the nitrone-oxaziridine rearrangement as a novel method for photochemical activation for the homolysis of alkoxyamine in nitroxide-mediated polymerization. The photoisomerization of the aldo-/ketonitrone-group into the oxaziridine one in 2,5-dihydroimidazole 3-oxide-based alkoxyamines was studied; the products of photolysis have been identified, and quantum yields were measured. Conversion of the nitrone group into the oxaziridine one was found to decrease the activation energy of alkoxyamine homolysis by ca. 10 kJ mol-1.

Unleashing the Power of PET-RAFT Polymerization: Journey from Porphyrin-Based Photocatalysts to Combinatorial Technologies and Advanced Bioapplications

The emergence of photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer polymerization (PET-RAFT) not only revolutionized the field of photopolymerization but also accelerated the development of porphyrin-based photocatalysts and their analogues. The continual expansion of the monomer family compatible with PET-RAFT polymerization enhances the range of light radiation that can be harnessed, providing increased flexibility in polymerization processes. Furthermore, the versatility of PET-RAFT polymerization extends beyond its inherent capabilities, enabling its integration with various technologies in diverse fields. This integration holds considerable promise for the advancement of biomaterials with satisfactory bioapplications. As researchers delve deeper into the possibilities afforded by PET-RAFT polymerization, the collaborative efforts of individuals from diverse disciplines will prove invaluable in unleashing its full potential. This Review presents a concise introduction to the fundamental principles of PET-RAFT, outlines the progress in photocatalyst development, highlights its primary applications, and offers insights for future advancements in this technique, paving the way for exciting innovations and applications.

Polymer-Coated Covalent Organic Frameworks as Porous Liquids for Gas Storage

Several synthetic methods have recently emerged to develop high-surface-area solid-state organic framework-based materials into free-flowing liquids with permanent porosity. The fluidity of these porous liquid (PL) materials provides them with advantages in certain storage and transport processes. However, most framework-based materials necessitate the use of cryogenic temperatures to store weakly bound gases such as H2, temperatures where PLs lose their fluidity. Covalent organic framework (COF)-based PLs that could reversibly form stable complexes with H2 near ambient temperatures would represent a promising development for gas storage and transport applications. We report here the development, characterization, and evaluation of a material with these remarkable characteristics based on Cu(I)-loaded COF colloids. Our synthetic strategy required tailoring conditions for growing robust coatings of poly(dimethylsiloxane)-methacrylate (PDMS-MA) around COF colloids using atom transfer radical polymerization (ATRP). We demonstrate exquisite control over the coating thickness on the colloidal COF, quantified by transmission electron microscopy and dynamic light scattering. The coated COF material was then suspended in a liquid polymer matrix to make a PL. CO2 isotherms confirmed that the coating preserved the general porosity of the COF in the free-flowing liquid, while CO sorption measurements using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed the preservation of Cu(I) coordination sites. We then evaluated the gas sorption phenomenon in the Cu(I)-COF-based PLs using DRIFTS and temperature-programmed desorption measurements. In addition to confirming that H2 transport is possible at or near mild refrigeration temperatures with these materials, our observations indicate that H2 diffusion is significantly influenced by the glass-transition temperature of both the coating and the liquid matrix. The latter result underscores an additional potential advantage of PLs in tailoring gas diffusion and storage temperatures through the coating composition.

Fe3O4/PMMA with Well-Arranged Structures Synthesized through Magnetic Field-Assisted Atom Transfer Radical Polymerization

Particle- or fiber-reinforced polymer composites with controlled orientations are attracting interest and applications producing innovative materials, biological constructs, and energy devices. To gain the controlled orientations, filed-assisted synthesis is widely selected for its easy operation and control. In this paper, we designed magnetic field-assisted equipment and synthesized a magnetic polymer composite Fe3O4/PMMA with a well-arranged layers structure by combining the magnetic field with atom transfer radical polymerization (ATRP). During the polymerization of polymer composites, the magnetic nanoparticles were surrounded by monomers. With the growth of polymer chains, the magnetic particles pushed polymer chains to move according to a specific direction and form a well-arranged structure under the magnetic fields. The existence of a well-arranged layered structure of the composites gives potential guidance for controlling the micro-structure by adding an extra field during the polymerization process. The experimental results provided a possible design to influence the macroscale properties through control of the micro-structure of polymer composites.

The thermodynamics and kinetics of depolymerization: what makes vinyl monomer regeneration feasible?

Depolymerization is potentially a highly advantageous method of recycling plastic waste which could move the world closer towards a truly circular polymer economy. However, depolymerization remains challenging for many polymers with all-carbon backbones. Fundamental understanding and consideration of both the kinetics and thermodynamics are essential in order to develop effective new depolymerization systems that could overcome this problem, as the feasibility of monomer generation can be drastically altered by tuning the reaction conditions. This perspective explores the underlying thermodynamics and kinetics governing radical depolymerization of addition polymers by revisiting pioneering work started in the mid-20th century and demonstrates its connection to exciting recent advances which report depolymerization reaching near-quantitative monomer regeneration at much lower temperatures than seen previously. Recent catalytic approaches to monomer regeneration are also explored, highlighting that this nascent chemistry could potentially revolutionize depolymerization-based polymer recycling in the future.

Determination of Reaction Kinetics by Time-Resolved Small-Angle X-ray Scattering during Polymerization-Induced Self-Assembly: Direct Evidence for Monomer-Swollen Nanoparticles

The kinetics of heterogeneous polymerization is determined directly using small-angle X-ray scattering (SAXS). This important advancement is exemplified for the synthesis of sterically-stabilized diblock copolymer nanoparticles by reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) in mineral oil at 90 °C. The principle of mass balance is invoked to derive a series of equations for the analysis of the resulting time-resolved SAXS patterns. Importantly, there is a continuous change in the X-ray scattering length density for the various components within the reaction mixture. This enables the volume fraction of unreacted BzMA monomer to be calculated at any given time point, which enables the polymerization kinetics to be monitored in situ directly without relying on supplementary characterization techniques. Moreover, SAXS enables the local concentration of both monomer and solvent within the growing swollen nanoparticles to be determined during the polymerization. Data analysis reveals that the instantaneous rate of BzMA polymerization is proportional to the local monomer concentration within the nanoparticles. In principle, this powerful new time-resolved SAXS approach can be applicable to other heterogeneous polymerization formulations.

Relating Structure to Properties in Non-Conjugated Pendant Electroactive Polymers

Non-conjugated pendant electroactive polymers (NCPEPs) are an emerging class of polymers that offer the potential of combining the desirable optoelectronic properties of conjugated polymers with the superior synthetic methodologies and stability of traditional non-conjugated polymers. Despite an increasing number of studies focused on NCPEPs, particularly on understanding fundamental structure-property relationships, no attempts have been made to provide an overview on established relationships to date. This review showcases selected reports on NCPEP homopolymers and copolymers that demonstrate how optical, electronic, and physical properties of the polymers are affected by tuning of key structural variables such as the chemical structure of the polymer backbone, molecular weight, tacticity, spacer length, the nature of the pendant group, and in the case of copolymers the ratios between different comonomers and between individual polymer blocks. Correlation of structural features with improved π-stacking and enhanced charge carrier mobility serve as the primary figures of merit in evaluating impact on NCPEP properties. While this review is not intended to serve as a comprehensive summary of all reports on tuning of structural parameters in NCPEPs, it highlights relevant established structure-property relationships that can serve as a guideline for more targeted design of novel NCPEPs in the future.

Synthesis and Fabrication of Betulin-Derived Polysulfide and Polysulfoxide Electrospun Fibers for Fruit Preservation

Plant-derived biocompounds play a crucial role in the field of renewable materials due to their sustainability as they can be converted into monomers for polymerization, comparable to numerous monomers obtained from petroleum. In this work, betulin, a triterpene derivative with antibacterial properties obtained from birch tree bark, was esterified to produce two varieties of α,ω-diene derivatives with different lengths of methylene spacers. These derivatives were then copolymerized with 2,2'-(ethylenedioxy)diethanethiol using thiol-ene photopolymerization. We optimized and confirmed the polymerization parameters such as solvents, catalysts, and monomer concentrations. These analyses allowed for the obtainment of polysulfides with a high molar mass of up to 38.9 kg/mol under the optimized conditions. Furthermore, the polysulfides were converted into polysulfoxides by using a dilute hydrogen peroxide solution. Thermal analysis of the obtained polymers revealed excellent thermal stability (up to 300 °C) and tunable glass transition temperatures depending on their molar mass and composition. We successfully produced fibers with a diameter of approximately 3.9 μm by using the electrospinning technique. The morphology and hydrophobicity of the fibers were analyzed by using scanning electron microscopy and water contact angle analysis. Plant-derived polymeric fibers exhibited good cellular biocompatibility and broad-spectrum antibacterial activity, making them promising candidates for applications in fruit preservation.

The synthesis of multifunctional cellulose graft alternating copolymers of 3,4-dihydrocoumarin and epoxides in DBU/DMSO/CO2 solvent system

Cellulose graft copolymers having well-defined structures could incorporate the characteristics of both the cellulose skeleton and side chains, providing a new method for the preparation functionalised cellulose derivatives. Herein, a series of multifunctional cellulose grafted, alternating 3,4-dihydrocoumarin (DHC) and epoxide (EPO) copolymers (cell-g-P(DHC-alt-EPO)) were prepared in a metal-free DBU/DMSO/CO2 solvent system without adding additional catalyst. Four examples of cell-g-P(DHC-alt-EPO) with tunable thermal and optical properties were synthesized by copolymerization of DHC with styrene oxide (SO), propylene oxide (PO), cyclohexene oxide (CHO) or furfuryl glycidyl ether (FGE) onto cellulose. The nonconjugated cell-g-P(DHC-alt-EPO) showed UV absorption properties with the maximum absorption peak at 282 nm and 295 nm and photoluminescence performance. A clustering-triggered emission mechanism was confirmed and consistent with DFT theoretical calculations. In DMSO solution, the copolymer (DHCSO5) with DP of 11.64 showed ACQ behaviour as the concentration increased. In addition, DHCSO5 had good antioxidant capacity with an instantaneous radical scavenging activity of 2,2-diphenyl-1-picrylhydrazine (DPPH) up to 65 % at a concentration of 40 mg/ ml and increased to 100 % after 30 min. Thus, the multifunctional cell-g-P(DHC-alt-EPO) materials had a variety of potential applications in the fields of fluorescent printing, bio-imaging, UV- shielding and antioxidants.

Fluoropolymer Nanoparticles Synthesized via Reversible-Deactivation Radical Polymerizations and Their Applications

Fluorinated polymeric nanoparticles (FPNPs) combine unique properties of fluorocarbon and polymeric nanoparticles, which has stimulated massive interest for decades. However, fluoropolymers are not readily available from nature, resulting in synthetic developments to obtain FPNPs via free radical polymerizations. Recently, while increasing cutting-edge directions demand tailored FPNPs, such materials have been difficult to access via conventional approaches. Reversible-deactivation radical polymerizations (RDRPs) are powerful methods to afford well-defined polymers. Researchers have applied RDRPs to the fabrication of FPNPs, enabling the construction of particles with improved complexity in terms of structure, composition, morphology, and functionality. Related examples can be classified into three categories. First, well-defined fluoropolymers synthesized via RDRPs have been utilized as precursors to form FPNPs through self-folding and solution self-assembly. Second, thermally and photoinitiated RDRPs have been explored to realize in situ preparations of FPNPs with varied morphologies via polymerization-induced self-assembly and cross-linking copolymerization. Third, grafting from inorganic nanoparticles has been investigated based on RDRPs. Importantly, those advancements have promoted studies toward promising applications, including magnetic resonance imaging, biomedical delivery, energy storage, adsorption of perfluorinated alkyl substances, photosensitizers, and so on. This Review should present useful knowledge to researchers in polymer science and nanomaterials and inspire innovative ideas for the synthesis and applications of FPNPs.

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.

Beauty of Explicit Dispersity (Đ) Equations in Controlled Polymerizations

Dispersity (Đ) as a critical parameter indicates the level of uniformity of the polymer molar mass or chain length. In the past several decades, the development of explicit equations for calculating Đ experiences a continual revolution. This viewpoint tracks the historical evolution of the explicit equations from living to reversible-deactivation polymerization systems. Emphasis is laid on displaying the charm of explicit Đ equations in batch reversible-deactivation radical polymerization (RDRP), with highlights of the relevant elegant mathematical manipulations. Some representative emerging applications enabled by the existing explicit equations are shown, involving nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (RAFT) polymerization systems. Stemming from the several outlined challenges and outlooks, sustained concerns about the explicit Đ equations are still highly deserved. It is expected that these equations will continue to play an important role not only in traditional polymerization kinetic simulation and design of experiments but also in modern intelligent manufacturing of precision polymers and classroom education.

Near-Infrared Light-Induced Reversible Deactivation Radical Polymerization: Expanding Frontiers in Photopolymerization

Photoinduced reversible deactivation radical polymerization (photo-RDRP) or photoinduced controlled/living radical polymerization has emerged as a versatile and powerful technique for preparing functional and advanced polymer materials under mild conditions by harnessing light energy. While UV and visible light (λ = 400-700 nm) are extensively employed in photo-RDRP, the utilization of near-infrared (NIR) wavelengths (λ = 700-2500 nm) beyond the visible region remains relatively unexplored. NIR light possesses unique properties, including enhanced light penetration, reduced light scattering, and low biomolecule absorption, thereby providing opportunities for applying photo-RDRP in the fields of manufacturing and medicine. This comprehensive review categorizes all known NIR light-induced RDRP (NIR-RDRP) systems into four mechanism-based types: mediation by upconversion nanoparticles, mediation by photocatalysts, photothermal conversion, and two-photon absorption. The distinct photoinitiation pathways associated with each mechanism are discussed. Furthermore, this review highlights the diverse applications of NIR-RDRP reported to date, including 3D printing, polymer brush fabrication, drug delivery, nanoparticle synthesis, and hydrogel formation. By presenting these applications, the review underscores the exceptional capabilities of NIR-RDRP and offers guidance for developing high-performance and versatile photopolymerization systems. Exploiting the unique properties of NIR light unlocks new opportunities for synthesizing functional and advanced polymer materials.

Microporous Block Copolymers Modified with Cu(II)-Coordinated Polyethylene Oxide-Substituted Silicas for Analytical Sensors

The influence of stable-to-self-condensation Cu(II)-coordinated polyoxyethylene-substituted silicas (ASiP-Cu-0.5) on the synthesis of microporous block copolymers (OBCs) whose structural feature is the existence of coplanar polyisocyanate blocks of acetal nature (O-polyisocyanates) and a flexible-chain component of amphiphilic nature was studied. The use of ASiP-Cu-0.5 increased the yield of O-polyisocyanate blocks and the microphase separation of OBC. The resulting OBCs turned out to be effective sorbents for the analytical reagents PAN and PHENAZO, which, being in the micropore cavity, interacted with copper(II) and magnesium ions. To reduce the thickness of the selective OBC layer ten-fold and simplify the technology for obtaining analytical test systems, polyethylene terephthalate was used as a substrate for applying OBC. It was found that the increased sensitivity of the resulting test systems was due to the fact that in thin reaction layers, the efficiency of the formation of O-polyisocyanate blocks noticeably increased.

Recent Advances in Polymerization-Induced Self-Assembly (PISA) Syntheses in Non-Polar Media

It is well-known that polymerization-induced self-assembly (PISA) is a powerful and highly versatile technique for the rational synthesis of colloidal dispersions of diblock copolymer nanoparticles, including spheres, worms or vesicles. PISA can be conducted in water, polar solvents or non-polar media. In principle, the latter formulations offer a wide range of potential commercial applications. However, there has been just one review focused on PISA syntheses in non-polar media and this prior article was published in 2016. The purpose of the current review article is to summarize the various advances that have been reported since then. In particular, PISA syntheses conducted using reversible addition-fragmentation chain-transfer (RAFT) polymerization in various n-alkanes, poly(α-olefins), mineral oil, low-viscosity silicone oils or supercritical CO2 are discussed in detail. Selected formulations exhibit thermally induced worm-to-sphere or vesicle-to-worm morphological transitions and the rheological properties of various examples of worm gels in non-polar media are summarized. Finally, visible absorption spectroscopy and small-angle X-ray scattering (SAXS) enable in situ monitoring of nanoparticle formation, while small-angle neutron scattering (SANS) can be used to examine micelle fusion/fission and chain exchange mechanisms.

Non-activated Esters as Reactive Handles in Direct Post-Polymerization Modification

Non-activated esters are prominently featured functional groups in polymer science, as ester functional monomers display great structural diversity and excellent compatibility with a wide range of polymerization mechanisms. Yet, their direct use as a reactive handle in post-polymerization modification has been typically avoided due to their low reactivity, which impairs the quantitative conversion typically desired in post-polymerization modification reactions. While activated ester approaches are a well-established alternative, the modification of non-activated esters remains a synthetic and economically valuable opportunity. In this review, we discuss past and recent efforts in the utilization of non-activated ester groups as a reactive handle to facilitate transesterification and aminolysis/amidation reactions, and the potential of the developed methodologies in the context of macromolecular engineering.

Plant-based Biomass/Polyvinyl Alcohol Gels for Flexible Sensors

Flexible sensors show great application potential in wearable electronics, human-computer interaction, medical health, bionic electronic skin and other fields. Compared with rigid sensors, hydrogel-based devices are more flexible and biocompatible and can easily fit the skin or be implanted into the body, making them more advantageous in the field of flexible electronics. In all designs, polyvinyl alcohol (PVA) series hydrogels exhibit high mechanical strength, excellent sensitivity and fatigue resistance, which make them promising candidates for flexible electronic sensing devices. This paper has reviewed the latest progress of PVA/plant-based biomass hydrogels in the construction of flexible sensor applications. We first briefly introduced representative plant biomass materials, including sodium alginate, phytic acid, starch, cellulose and lignin, and summarized their unique physical and chemical properties. After that, the design principles and performance indicators of hydrogel sensors are highlighted, and representative examples of PVA/plant-based biomass hydrogel applications in wearable electronics are illustrated. Finally, the future research is briefly prospected. We hope it can promote the research of novel green flexible sensors based on PVA/biomass hydrogel.

Robust Strategy to Improve the Compatibility between Incorporated Upconversion Nanoparticles and the Bulk Transparent Polymer Matrix

Traditional transparent polymer nanocomposites combined with functional fluorescent inorganic nanofillers are promising for many advanced optical applications. However, the aggregation of the incorporated functional nanoparticles results in light scattering and will decrease the transparency of nanocomposites, which will restrain the application of the transparent nanocomposites. Herein, a robust synthesis strategy was proposed to modify upconversion nanoparticles (UCNPs) with polymethyl methacrylate (PMMA) to form UCNP@PMMA core@shell nanocomposites though metal-free photoinduced surface-initiated atom transfer radical polymerization (photo-SI-ATRP), and thus, the dispersity of UCNP@PMMA and the interface compatibility between the surface of UCNPs and the bulk PMMA matrix was greatly improved. The obtained PMMA nanocomposites possess high transparency and show strong upconversion photoluminescence properties, which promises great opportunities for application in 3D display and related optoelectronic fields. This strategy could also be applied to fabricate other kinds of functional transparent polymer nanocomposites with inorganic nanoparticles uniformly dispersed.

A Supported Catalyst that Enables the Synthesis of Colorless CO2 -Polyols with Ultra-Low Molecular Weight

Ultra-low molecular weight (ULMW) CO2 -polyols with well-defined hydroxyl end groups represent useful soft segments for the preparation of high-performance polyurethane foams. However, owing to the poor proton tolerance of catalysts towards CO2 /epoxide telomerization, it remains challenging to synthesize ULMW yet colorless CO2 -polyols. Herein, we propose an immobilization strategy of constructing supported catalysts by chemical anchoring of aluminum porphyrin on Merrifield resin. The resulting supported catalyst displays both extremely high proton tolerance (≈8000 times the equivalents of metal centers) and independence of cocatalyst, affording CO2 -polyols with ULMW (580 g mol-1 ) and high polymer selectivity (>99 %). Moreover, the ULMW CO2 -polyols with various architectures (tri-, quadra-, and hexa-arm) can be obtained, suggesting the wide proton universality of supported catalysts. Notably, benefiting from the heterogeneous nature of the supported catalyst, colorless products can be facilely achieved by simple filtration. The present strategy provides a platform for the synthesis of colorless ULMW polyols derived from not only CO2 /epoxides, but also lactone, anhydrides etc. or their combinations.

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.

Effective Interaction between Homo- and Heteropolymer Block of Poly(n-butyl acrylate)-b-poly(methyl methacrylate-r-styrene) Diblock Copolymers

We investigated the segregation behavior of a molten diblock copolymer, poly(n-butyl acrylate)-b-poly(methyl methacrylate-r-styrene) (PBA-b-P(MMA-r-S)), wherein styrene (S) is incorporated as a comonomer in the second block to modulate the effective interaction between homopolymer and a random copolymer block. The temperature dependence of the effective interaction parameter χeff between n-butyl acrylate (BA) and the average monomer of the MMA-r-S random block was evaluated from small-angle X-ray scattering (SAXS) analysis using the random phase approximation (RPA) approach. The calculated χeff, as a function of the styrene fraction in the random copolymer block, shows a good agreement with the mean-field binary interaction model. This consistency indicates that the effective interaction between component BA and the average monomer of the random copolymer block is smaller than the interactions between pure components (χBA,MMA,χBA,S). The present study suggests that the introduction of a random copolymer block to a block copolymer can effectively reduce the degree of incompatibility of the block copolymer system without altering the constituent species, which may serve as a viable methodology in designing novel thermoplastic elastomers based on triblock or multiblock copolymers.

Molecularly Imprinted Polymer-Based Sensors for the Detection of Skeletal- and Cardiac-Muscle-Related Analytes

Molecularly imprinted polymers (MIPs) are synthetic polymers with specific binding sites that present high affinity and spatial and chemical complementarities to a targeted analyte. They mimic the molecular recognition seen naturally in the antibody/antigen complementarity. Because of their specificity, MIPs can be included in sensors as a recognition element coupled to a transducer part that converts the interaction of MIP/analyte into a quantifiable signal. Such sensors have important applications in the biomedical field in diagnosis and drug discovery, and are a necessary complement of tissue engineering for analyzing the functionalities of the engineered tissues. Therefore, in this review, we provide an overview of MIP sensors that have been used for the detection of skeletal- and cardiac-muscle-related analytes. We organized this review by targeted analytes in alphabetical order. Thus, after an introduction to the fabrication of MIPs, we highlight different types of MIP sensors with an emphasis on recent works and show their great diversity, their fabrication, their linear range for a given analyte, their limit of detection (LOD), specificity, and reproducibility. We conclude the review with future developments and perspectives.

Circularity in polymers: addressing performance and sustainability challenges using dynamic covalent chemistries

The circularity of current and future polymeric materials is a major focus of fundamental and applied research, as undesirable end-of-life outcomes and waste accumulation are global problems that impact our society. The recycling or repurposing of thermoplastics and thermosets is an attractive solution to these issues, yet both options are encumbered by poor property retention upon reuse, along with heterogeneities in common waste streams that limit property optimization. Dynamic covalent chemistry, when applied to polymeric materials, enables the targeted design of reversible bonds that can be tailored to specific reprocessing conditions to help address conventional recycling challenges. In this review, we highlight the key features of several dynamic covalent chemistries that can promote closed-loop recyclability and we discuss recent synthetic progress towards incorporating these chemistries into new polymers and existing commodity plastics. Next, we outline how dynamic covalent bonds and polymer network structure influence thermomechanical properties related to application and recyclability, with a focus on predictive physical models that describe network rearrangement. Finally, we examine the potential economic and environmental impacts of dynamic covalent polymeric materials in closed-loop processing using elements derived from techno-economic analysis and life-cycle assessment, including minimum selling prices and greenhouse gas emissions. Throughout each section, we discuss interdisciplinary obstacles that hinder the widespread adoption of dynamic polymers and present opportunities and new directions toward the realization of circularity in polymeric materials.

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.

Design of Microstructure-Engineered Polymers for Energy and Environmental Conservation

With the ever-growing demand for sustainability, designing polymeric materials using readily accessible feedstocks provides potential solutions to address the challenges in energy and environmental conservation. Complementing the prevailing strategy of varying chemical composition, engineering microstructures of polymer chains by precisely controlling their chain length distribution, main chain regio-/stereoregularity, monomer or segment sequence, and architecture creates a powerful toolbox to rapidly access diversified material properties. In this Perspective, we lay out recent advances in utilizing appropriately designed polymers in a wide range of applications such as plastic recycling, water purification, and solar energy storage and conversion. With decoupled structural parameters, these studies have established various microstructure-function relationships. Given the progress outlined here, we envision that the microstructure-engineering strategy will accelerate the design and optimization of polymeric materials to meet sustainability criteria.

Effects of Alkyl Ester Chain Length on the Toughness of PolyAcrylate-Based Network Materials

Polyacrylate-based network materials are widely used in various products owing to their facile synthesis via radical polymerization reactions. In this study, the effects of alkyl ester chains on the toughness of polyacrylate-based network materials were investigated. Polymer networks were fabricated via the radical polymerization of methyl acrylate (MA), ethyl acrylate (EA), and butyl acrylate (BA) in the presence of 1,4-butanediol diacrylate as a crosslinker. Differential scanning calorimetry and rheological measurements revealed that the toughness of MA-based networks drastically increased compared with that of EA- and BA-based networks; the fracture energy of the MA-based network was approximately 10 and 100 times greater than that of EA and BA, respectively. The high fracture energy was attributed to the glass transition temperature of the MA-based network (close to room temperature), resulting in large energy dissipation via viscosity. Our results set a new basis for expanding the applications of polyacrylate-based networks as functional materials.

Multiblock copolymer synthesis via RAFT emulsion polymerization

A multiblock copolymer is a polymer of a specific structure that consists of multiple covalently linked segments, each comprising a different monomer type. The control of the monomer sequence has often been described as the "holy grail" of synthetic polymer chemistry, with the ultimate goal being synthetic access to polymers of a "perfect" structure, where each monomeric building block is placed at a desired position along the polymer chain. Given that polymer properties are intimately linked to the microstructure and monomer distribution along the constituent chains, it goes without saying that there exist seemingly endless opportunities in terms of fine-tuning the properties of such materials by careful consideration of the length of each block, the number and order of blocks, and the inclusion of monomers with specific functional groups. The area of multiblock copolymer synthesis remains relatively unexplored, in particular with regard to structure-property relationships, and there are currently significant opportunities for the design and synthesis of advanced materials. The present review focuses on the synthesis of multiblock copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization implemented as aqueous emulsion polymerization. RAFT emulsion polymerization offers intriguing opportunities not only for the advanced synthesis of multiblock copolymers, but also provides access to polymeric nanoparticles of specific morphologies. Precise multiblock copolymer synthesis coupled with self-assembly offers material morphology control on length scales ranging from a few nanometers to a micrometer. It is imperative that polymer chemists interact with physicists and material scientists to maximize the impact of these materials of the future.

Star-Shaped Thermoplastic Elastomers Prepared via RAFT Polymerization

Styrene-based thermoplastic elastomers (TPEs) demonstrate excellent overall performance and account for the largest industrial output. The traditional methods of preparation styrene-based thermoplastic elastomers mainly focused on anionic polymerization, and strict equipment conditions were required. In recent years, controlled/living radical polymerization (CRP) has developed rapidly, enabling the synthesis of polymers with various complex topologies while controlling their molecular weight. Herein, a series of core crosslinked star-shaped poly(styrene-b-isoprene-b-styrene)s (SISs) was synthesized for the first time via reversible addition-fragmentation chain transfer (RAFT) polymerization. Meanwhile, linear triblock SISs with a similar molecular weight were synthesized as a control. We achieved not only the controlled/living radical polymerization of isoprene but also investigated the factors influencing the star-forming process. By testing the mechanical and thermal properties and characterizing the microscopic fractional phase structure, we found that both the linear and star-shaped SISs possessed good tensile properties and a certain phase separation structure, demonstrating the characteristics of thermoplastic elastomers.

An electrochemically mediated ATRP synthesis of lignin-g-PDMAPS UCST-thermoresponsive polymer

It is a promising idea to graft zwitterionic polymers onto lignin and prepare lignin-grafted-poly [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (Lignin-g-PDMAPS) thermosensitive polymer with the upper critical solution temperature (UCST). In this paper, an electrochemically mediated atom transfer radical polymerization (eATRP) method was used to prepare Lignin-g-PDMAPS. The structure and property of the Lignin-g-PDMAPS polymer were characterized by the fourier transform infrared spectrum (FT-IR), nuclear magnetic resonance (NMR), X-ray electron spectroscopy (XPS), dynamic light scattering (DLS), differential scanning calorimeter (DSC). Furthermore, the effect of catalyst structure, applied potential, amount of Lignin-Br, Lignin-g-PDMAPS concentration, NaCl concentration on UCST of Lignin-g-PDMAPS were investigated. It was worth noting that polymerization was well controlled when the ligand was tris (2-aminoethyl) amine (Me₆TREN), applied potential was -0.38 V and the amount of Lignin-Br was 100 mg. And the UCST of the Lignin-g-PDMAPS aqueous solution (1 mg/ml) was 51.47 °C, the molecular weight was 8987 g/mol, and the particle size was 318 nm. It was also found that the UCST increased and the particle size decreased with the Lignin-g-PDMAPS polymer concentration increased, and the UCST decreased and the particle size increased with the NaCl concentration increases. This work investigated UCST-thermoresponsive polymer which possessed lignin main chain combining the zwitterionic side chain, and provided a new way for development of lignin based UCST-thermoresponsive materials and medical carrier materials, in addition to expand the scope of eATRP.

Polymer Colloids: Current Challenges, Emerging Applications, and New Developments

Polymer colloids are complex materials that have the potential to be used in a vast array of applications. One of the main reasons for their continued growth in commercial use is the water-based emulsion polymerization process through which they are generally synthesized. This technique is not only highly efficient from an industrial point of view but also extremely versatile and permits the large-scale production of colloidal particles with controllable properties. In this perspective, we seek to highlight the central challenges in the synthesis and use of polymer colloids, with respect to both existing and emerging applications. We first address the challenges in the current production and application of polymer colloids, with a particular focus on the transition toward sustainable feedstocks and reduced environmental impact in their primary commercial applications. Later, we highlight the features that allow novel polymer colloids to be designed and applied in emerging application areas. Finally, we present recent approaches that have used the unique colloidal nature in unconventional processing techniques.

Single-chain polymer nanoparticles in biomedical applications

Single-chain polymer nanoparticles (SCNPs) are a well-defined and uniquely sized class of polymer nanoparticles. The advances in polymer science over the past decades have enabled the development of a variety of intramolecular crosslinking systems, leading to particles in the 5-20 nm size regime. Which is aligned with the size regime of proteins and therefore making SCNPs an interesting class of NPs for biomedical applications. The high modularity of SCNP design and the ease of their functionalization have led to growing research interest. In this review, we describe different crosslinking systems, as well as the preparation of functional SCNPs and the variety of biomedical applications that have been explored.