Toward Sustainable Polymer Materials for Rechargeable Batteries: Utilizing Natural Feedstocks and Recycling/Upcycling of Polymer Waste.

The ever-increasing demand for rechargeable battery systems in the era of electric vehicles has spurred extensive research into developing polymeric components for batteries, such as separators, polymer electrolytes, and binders. However, current battery systems rely on expensive and nonrenewable resources, which potentially have a negative environmental impact. Therefore, polymer materials derived from natural resources have gained significant attention, primarily due to their cost-effective and environmentally sustainable features. Moreover, natural feedstocks often possess highly polar functional groups and high molecular weights, offering desirable electro-chemo-mechanical features when applied as battery materials. More recently, various recycling and upcycling strategies for polymeric battery components have also been proposed given the substantial waste generation from end-of-life batteries. Recycling polymeric materials includes an overall process of recovering the components from spent batteries followed by regeneration into new materials. Polymer upcycling into battery materials involves transforming daily-used plastic waste into high-value-added battery components. This review aims to give a state-of-the-art overview of contemporary methods to develop sustainable polymeric materials and recycling/upcycling strategies for various battery applications.

Roll-to-plate 0.1-second shear-rolling process at elevated temperature for highly aligned nanopatterns.

The shear-rolling process is a promising directed self-assembly method that can produce high-quality sub-10 nm block copolymer line-space patterns cost-effectively and straightforwardly over a large area. This study presents a high temperature (280 °C) and rapid (~0.1 s) shear-rolling process that can achieve a high degree of orientation in a single process while effectively preventing film delamination, that can be applied to large-area continuous processes. By minimizing adhesion, normal forces, and ultimate shear strain of the polydimethylsiloxane pad, shearing was successfully performed without peeling up to 280 °C at which the chain mobility significantly increases. This method can be utilized for various high-χ block copolymers and surface neutralization processes. It enables the creation of block copolymer patterns with a half-pitch as small as 8 nm in a unidirectional way. Moreover, the 0.1-second rapid shear-rolling was successfully performed on long, 3-inch width polyimide flexible films to validate its potential for the roll-to-roll process.

Light-Scattering Analysis of Drying Behavior in Suspension Droplets with Silica and Polystyrene Particles and a Hydrosoluble Polymer.

The coffee-ring structure, which is the final drying pattern of a sessile suspension droplet, is a key factor in controlling the uniformity of the particulate deposits in various coatings. Two light-scattering methods, diffusing wave spectroscopy (DWS) and multispeckle DWS (MSDWS), were used to quantitatively distinguish temporal changes in particle mobility in evaporating suspension droplets containing micrometer-sized silica and polystyrene (PS) particles. The characteristic particle mobility was measured in terms of the mean square displacement in the early stage of drying, and the local particle dynamics around the edge and center regimes of the droplets during drying were analyzed using MSDWS. Hydroxyethyl cellulose (HEC), a hydrosoluble polymer, was added to the silica and PS suspensions to further investigate its role in suppressing or enhancing coffee-ring patterns based on particle-polymer interactions. Consequently, dried microstructures can be directly correlated with real-time drying dynamics, as well as the interactions between solutes by comprehensive light-scattering methods.

Nanostructured doping of WSe2via block copolymer patterns and its self-powered photodetector application.

Transition metal dichalcogenides (TMDs), e.g., MoS2, MoSe2, ReS2, and WSe2, are effective materials for advanced optoelectronics owing to their intriguing optical, structural, and electrical properties. Various approaches for manipulating the surface of the TMDs have been suggested to unleash the optoelectronic potential of the TMDs. Herein, we employed the self-assembly of the poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer (BCP) to prepare a nanoporous pattern and generate nanostructured charge-transfer p-doping on the WSe2 surface, maximizing the depletion region in the absorber layer. After the spin coating and thermal annealing of PS-b-PMMA, followed by the selective etching of PMMA cylindrical microdomains using oxygen reactive-ion plasma, nanopatterned WOx with high electron affinity was grown on the WSe2 surface, forming a three-dimensional homojunction. The nanopatterned WOx significantly expanded the depletion region in the WSe2 layer, thus enhancing optoelectronic performance and self-powered photodetection. The proposed approach based on the nanostructured doping of the TMDs via BCP nanolithography can help create a promising platform for highly functional optoelectrical devices.

Topical methylene blue nanoformulation for the photodynamic therapy of acne vulgaris.

Acne vulgaris is a common skin disease caused by multifactorial reasons involving excessive sebum secretion and inflammation by Cutibacterium acnes (C. acnes). Various conventional therapies are available for the treatment of acne vulgaris; however, topical photodynamic therapy (PDT) has attracted much attention because of its great potential for sebum-reducing, anti-inflammatory, and antimicrobial activities. Although 5-aminolevulinic acid (ALA) has been broadly used as a photosensitizer for topical PDT, it has several limitations such as long incubation time, pain, and post-inflammatory hyperpigmentation. Here, we report a biocompatible nanoformulation consisting of methylene blue and salicylic acid (MBSD), as a potent PDT and acne therapeutics, enclosed within oleic acid. Photoactivated MBSD showed antimicrobial activity against C. acnes along with long-term stability. When 24 patients with acne were treated with MBSD and light irradiation 5 times at 1-week intervals, MBSD-based PDT exhibited a remarkable reduction in acne lesions and sebum production. In addition, the therapeutic procedure was painless and safe, without any adverse events. Therefore, MBSD is a promising topical PDT agent for biocompatible, safe, and effective acne treatment.

Sulfenyl Chlorides: An Alternative Monomer Feedstock from Elemental Sulfur for Polymer Synthesis.

A polymerization methodology is reported using sulfur monochloride (S2Cl2) as an alternative feedstock for polymeric materials. S2Cl2 is an inexpensive petrochemical derived from elemental sulfur (S8) but has numerous advantages as a reactive monomer for polymerization vs S8. This new process, termed sulfenyl chloride inverse vulcanization, exploits the high reactivity and miscibility of S2Cl2 with a broad range of allylic monomers to prepare soluble, high molar-mass linear polymers, segmented block copolymers, and crosslinked thermosets with greater synthetic precision than achieved using classical inverse vulcanization. This step-growth addition polymerization also allows for preparation of a new class of thiol-free, inexpensive, highly optically transparent thermosets (α = 0.045 cm-1 at 1310 nm), which exhibit among the best optical transparency and low birefringence relative to commodity optical polymers, while possessing a higher refractive index (n > 1.6) in the visible and near-infrared spectra. The fabrication of large-sized optical components is also demonstrated.

Controlled growth of redox polymer network on single enzyme molecule for stable and sensitive enzyme electrode.

The electrochemical applications of enzymes are often hampered by poor enzyme stability and low electron conductivity. In this work, a novel enzyme nanogel based on atom transfer radical polymerization (ATRP) has been developed for highly sensitive detection of glucose based on ferrocene (Fc) embedded in crosslinked polymer network nanogel. Enzyme surfaces are successively modified with Br initiator, and then in situ atom transfer radical polymerization (ATRP) was performed to build up crosslinked polyacrylamide network. The resulting single enzyme nanogel (ATRP-SEG) is uniform in size fairly. ATRP-SEG reveals bi-phasic inactivation, and the half-life of stable ATRP-SEG after 18-day incubation at 50 °C is 47 days, which is 197 times longer than that of free Gox (5.7 h). By introducing a ferrocene (Fc) containing redox polymer, poly(acrylamide-co-vinylferrocene), the half-life of Fc-ATRP-SEG after 18-day incubation at 50 °C is 49 days. Fc-ATRP-SEG is used for preparation of glucose-sensing electrode, and the sensitivity of Fc-ATRP-SEG electrode is 111 µA cm-2 mM-1, which is 366 and 1270 times higher than those of free GOx (0.303 µA cm-2 mM-1) and ATRP-SEG (0.0874 µA cm-2 mM-1), respectively. Fc-ATRP-SEG electrode maintained 90% of initial current density under 4 °C storage condition and repetitive usages every day for 7 days. Even the electrode repeatedly used in continuous harsh condition (250 rpm, room temperature), the current density maintained 96% after 12 h incubation at operational condition.

Loop and Bridge Conformations of ABA Triblock Comb Copolymers: A Conformational Assessment for Molecular Composites.

We computationally investigate the conformational behavior, "bridging" chain, between different the phase-separated domains vs "looping" chain on the same domain, for two chain architectures of ABA triblock copolymers, one with a linear architecture (L-TBC) and the other with comb architecture (C-TBC) at various segregation regimes using dissipative particle dynamics (DPD) simulations. The power-law relation between the bridge fraction (Φ) and the interaction parameter (χ) for C-TBC is found to be Φ∼χ-1.6 in the vicinity of the order-disorder transition (χODT), indicating a drastic conversion from the bridge to the loop conformation. When χ further increases, the bridge-loop conversions slow down to have the power law, Φ∼χ-0.18, approaching the theoretical power law Φ∼χ-1/9 predicted in the strong segregation limit. The conformational assessment conducted in the present study can provide a strategy of designing optimal material and processing conditions for triblock copolymer either with linear or comb architecture to be used for thermoplastic elastomer or molecular nanocomposites.

Optimizing Chain Topology of Bottle Brush Copolymer for Promoting the Disorder-to-Order Transition.

The order-disorder transitions (ODT) of core-shell bottle brush copolymer and its structural isomers were investigated by dissipative particle dynamics simulations and theoretically by random phase approximation. Introducing a chain topology parameter λ which parametrizes linking points between M diblock chains each with N monomers, the degree of incompatibility at ODT ((χN)ODT; χ being the Flory-Huggins interaction parameter between constituent monomers) was predicted as a function of chain topology parameter (λ) and the number of linked diblock chains per bottle brush copolymer (M). It was found that there exists an optimal chain topology about λ at which (χN)ODT gets a minimum while the domain spacing remains nearly unchanged. The prediction provides a theoretical guideline for designing an optimal copolymer architecture capable of forming sub-10 nm periodic structures even with non-high χ components.

Metal complexation-mediated stable and biocompatible nanoformulation of clinically approved near-infrared absorber for improved tumor targeting and photonic theranostics.

Indocyanine green (ICG) is a clinically approved dye that has shown great promise as a phototheranostic material with fluorescent, photoacoustic and photothermal responses in the near-infrared region. However, it has certain limitations, such as poor photostability and non-specific binding to serum proteins, subjected to rapid clearance and decreased theranostic efficacy in vivo. This study reports stable and biocompatible nanoparticles of ICG (ICG-Fe NPs) where ICG is electrostatically complexed with an endogenously abundant metal ion (Fe3+) and subsequently nanoformulated with a clinically approved polymer surfactant, Pluronic F127. Under near-infrared laser irradiation, ICG-Fe NPs were found to be more effective for photothermal temperature elevation than free ICG molecules owing to the improved photostability. In addition, ICG-Fe NPs showed the markedly enhanced tumor targeting and visualization with photoacoustic/fluorescent signaling upon intravenous injection, attributed to the stable metal complexation that prevents ICG-Fe NPs from releasing free ICG before tumor targeting. Under dual-modal imaging guidance, ICG-Fe NPs could successfully potentiate photothermal therapy of cancer by applying near-infrared laser irradiation, holding potential as a promising nanomedicine composed of all biocompatible ingredients for clinically relevant phototheranostics.

Effect of Silica Nanoparticles Blocked with Epoxy Groups on the Crosslinking and Surface Properties of PEG Hydrogel Films.

Silica nanoparticles (G-SiNPs) blocked with 3-glycidoxypropyl trimethoxysilane (GPTS) were newly applied to hydrogel films for improving film coating properties and to distribute the epoxy groups on the film surface. The effects of the content of epoxy-functionalized G-SiNPs on the crosslinking features by photo-induced radical polymerization and the surface mechanical properties of the hydrogel films containing poly(ethylene glycol) dimethacrylate (PEGDMA) and glycidyl methacrylate (GMA) were investigated. The real-time elastic modulus of various PEG hydrogel mixtures with prepared particles was monitored using a rotational rheometer. The distribution of epoxy groups on the crosslinked film surface was directly and indirectly estimated by the elemental analysis of Si and Br. The surface mechanical properties of various hydrogel films were measured by nano-indentation and nano-scratch tests. The relationship between the rheological and surface properties of PEG-based hydrogel films suggests that the use of small amounts of G-SiNPs enhances the surface hardness and crosslinked network of the film and uniformly distributes sufficient epoxy groups on the film surface for further coating applications.

Photoechogenic Inflatable Nanohybrids for Upconversion-Mediated Sonotheranostics.

Hybrid nanostructures are promising for ultrasound-triggered drug delivery and treatment, called sonotheranostics. Structures based on plasmonic nanoparticles for photothermal-induced microbubble inflation for ultrasound imaging exist. However, they have limited therapeutic applications because of short microbubble lifetimes and limited contrast. Photochemistry-based sonotheranostics is an attractive alternative, but building near-infrared (NIR)-responsive echogenic nanostructures for deep tissue applications is challenging because photolysis requires high-energy (UV-visible) photons. Here, we report a photochemistry-based echogenic nanoparticle for in situ NIR-controlled ultrasound imaging and ultrasound-mediated drug delivery. Our nanoparticle has an upconversion nanoparticle core and an organic shell carrying gas generator molecules and drugs. The core converts low-energy NIR photons into ultraviolet emission for photolysis of the gas generator. Carbon dioxide gases generated in the tumor-penetrated nanoparticle inflate into microbubbles for sonotheranostics. Using different NIR laser power allows dual-modal upconversion luminescence planar imaging and cross-sectional ultrasonography. Low-frequency (10 MHz) ultrasound stimulated microbubble collapse, releasing drugs deep inside the tumor through cavitation-induced transport. We believe that the photoechogenic inflatable hierarchical nanostructure approach introduced here can have broad applications for image-guided multimodal theranostics.

Segmented Polyurethanes and Thermoplastic Elastomers from Elemental Sulfur with Enhanced Thermomechanical Properties and Flame Retardancy.

The production of elemental sulfur from petroleum refining has created a technological opportunity to increase the valorization of elemental sulfur by the creation of high-performance sulfur based plastics with improved thermomechanical properties, elasticity and flame retardancy. We report on a synthetic polymerization methodology to prepare the first example of sulfur based segmented multi-block polyurethanes (SPUs) and thermoplastic elastomers that incorporate an appreciable amount of sulfur into the final target material. This approach applied both the inverse vulcanization of S8 with olefinic alcohols and dynamic covalent polymerizations with dienes to prepare sulfur polyols and terpolyols that were used in polymerizations with aromatic diisocyanates and short chain diols. Using these methods, a new class of high molecular weight, soluble block copolymer polyurethanes were prepared as confirmed by Size Exclusion Chromatography, NMR spectroscopy, thermal analysis, and microscopic imaging. These sulfur-based polyurethanes were readily solution processed into large area free standing films where both the tensile strength and elasticity of these materials were controlled by variation of the sulfur polyol composition. SPUs with both high tensile strength (13-24 MPa) and ductility (348 % strain at break) were prepared, along with SPU thermoplastic elastomers (578 % strain at break) which are comparable values to classical thermoplastic polyurethanes (TPUs). The incorporation of sulfur into these polyurethanes enhanced flame retardancy in comparison to classical TPUs, which points to the opportunity to impart new properties to polymeric materials as a consequence of using elemental sulfur.

Self-Assembly of 2D Gold Nanoparticle Superlattice in a Polymer Vesicle Layer Driven by Hydrophobic Interaction.

Self-assembly of gold nanoparticles (AuNPs) into highly ordered superstructures provides a promising route toward fabricating materials with new functionalities or enhanced physical properties. Although self-assembly of AuNPs has garnered significant research attention recently, a highly ordered superlattice of AuNPs under a low concentration in a confined geometry formed by nonfunctionalized materials has not been reported. Herein, we investigate the self-assembly of a 2D AuNPs superlattice in a polymer vesicle layer using hydrophobic interactions, which exhibits centered rectangular lattice symmetry. To create the highly ordered AuNPs superlattice, the P(EGx-b-iPGEy) block copolymers that form the thickness of the hydrophobic vesicle layer comparable to the size of the AuNP are used as a template to control the AuNP degree of freedom. To the best of our knowledge, this study provides the first demonstration of a centered rectangular structure formation of AuNPs at the vesicle layer in 2D confined geometry.

Shear-Rolling Process for Unidirectionally and Perpendicularly Oriented Sub-10-nm Block Copolymer Patterns on the 4 in Scale.

Shear alignment of the block copolymer (BCP) thin film is one of the promising directed self-assembly (DSA) methodologies for the unidirectional alignment of sub-10 nm microdomains of BCPs for next-generation nanolithography and nanowire-grid polarizers. However, because of the differences in the surface/interfacial energies at the top surface/bottom interface, the shear-induced ordering of BCP nanopatterns has been restricted to BCPs with spherical and cylindrical nanopatterns and cannot be realized for high-aspect-ratio perpendicular lamellar structures, which is essential for practical application to semiconductor pattern processes. It is still a difficult challenge to fabricate the unidirectional alignment in a short time over a large area. In this study, we propose an approach for combining the shear-rolling process with the filtered plasma treatment of BCP films for the fabrication of unidirectionally aligned and perpendicularly oriented lamellar nanostructures. This approach enables fabrication within 1 min on a 4 in scale. We treated filtered plasma on the BCP film for perpendicular orientation and executed the hot-rolling process with different roller and stage speeds. Large-scale shear was generated only at the location where the BCP film was in contact with both the roller and stage, effectively applying shear stress to a large area of the BCP film within a short time. The repeated application of this shear-rolling process can achieve a higher level of unidirectional alignment. Our aligned BCP vertical lamellae were used to fabricate a high-aspect-ratio sub-10-nm-wide metallic nanowire array via dry/wet processes. In addition, shear-rolling with chemoepitaxy patterns can achieve higher orientational order and lower defectivity.

Ligand-Assisted Direct Photolithography of Perovskite Nanocrystals Encapsulated with Multifunctional Polymer Ligands for Stable, Full-Colored, High-Resolution Displays.

Micropatterns with a high stability, definition, and resolution are an absolute requirement in advanced display technology. Herein, patternable perovskite nanocrystals (PNCs) with excellent stability were prepared by exchanging pristine ligands with multifunctional polymer ligands, poly(2-cinnamoyloxyethyl methacrylate). The polymer backbone contains a cinnamoyl group that has been widely employed as a photo-cross-linker under 365 nm UV irradiation. Also, the terminal group is readily adjustable among NH3Cl, NH3Br, and NH3I, allowing us to obtain multicolored PNCs via instant anion exchange. Furthermore, the resulting ligand exchanged PNCs exhibited enhanced stability toward polar solvents without any undesirable influence on the structural or optical properties of the PNCs. Using anion exchanged PNCs, RGB microarrays with a subpixel size of 10 µm × 40 µm were successfully demonstrated. Our results highlight the versatility and feasibility of a simplified patterning strategy for nanomaterials, which can be generally applied in the fabrication of various optoelectronic devices.

Janus Graphene Oxide Sheets with Fe3O4 Nanoparticles and Polydopamine as Anodes for Lithium-Ion Batteries.

In this study, a one-step process to fabricate "Janus"-structured nanocomposites with iron oxide (Fe3O4) nanoparticles (Fe3O4 NPs) and polydopamine (PDA) on each side of a graphene oxide (GO) nanosheet using the Langmuir-Schaefer technique has been proposed. The Fe3O4 NPs-GO hybrid is used as a high-capacity active material, while PDA is added as a binder due to its unique wet-resistant adhesive property. The transmission electron microscopy image shows a superlattice-like out-of-plane section of the multilayered nanocomposite, which maximizes the density of the composite materials. Grazing-incidence small-angle X-ray scattering results combined with scanning electron microscopy images confirm that the multilayered Janus composite exhibits an in-plane hexagonal array structure of closely packed Fe3O4 NPs. This Janus multilayered structure is expected to maximize the amount of active material in a specific volume and reduce volume changes caused by the conversion reaction of Fe3O4 NPs. According to the electrochemical results, the Janus multilayer electrode delivers an excellent capacity of ∼903 mAh g-1 at a current density of 200 mA g-1 and a reversible capacity of ∼639 mAh g-1 at 1 A g-1 up to the 1800th cycle, indicating that this Janus composite can be a promising anode for Li-ion batteries.

Molecular Weight Dependent Morphological Transitions of Bottlebrush Block Copolymer Particles: Experiments and Simulations.

The molecular weights and chain rigidities of block copolymers can strongly influence their self-assembly behavior, particularly when the block copolymers are under confinement. We investigate the self-assembly of bottlebrush block copolymers (BBCPs) confined in evaporative emulsions with varying molecular weights. A series of symmetric BBCPs, where polystyrene (PS) and polylactide (PLA) side-chains are grafted onto a polynorbornene (PNB) backbone, are synthesized with varying degrees of polymerization of the PNB (NPNB) ranging from 100 to 300. Morphological transitions from onion-like concentric particles to striped ellipsoids occur as the NPNB of the BBCP increases above 200, which is also predicted from coarse-grained simulations of BBCP-containing droplets by an implicit solvent model. This transition is understood by the combined effects of (i) an elevated entropic penalty associated with bending lamella domains of large molecular weight BBCP particles and (ii) the favorable parallel alignment of the backbone chains at the free surface. Furthermore, the morphological evolutions of onion-like and ellipsoidal particles are compared. Unlike the onion-like BBCP particles, ellipsoidal BBCP particles are formed by the axial development of ring-like lamella domains on the particle surface, followed by the radial propagation into the particle center. Finally, the shape anisotropies of the ellipsoidal BBCP particles are analyzed as a function of particle size. These BBCP particles demonstrate promising potential for various applications that require tunable rheological, optical, and responsive properties.

Bottlebrush Copolymer as Surface Neutralizer for Vertical Alignment of Block Copolymer Nanodomains in Thin Films.

Herein we designed bottlebrush copolymers for use as a neutral additive to block copolymer (BCP) thin films in which they are segregated to the interfaces via architectural effects and produce nonpreferential interfaces to induce perpendicular orientation of BCP microdomains. Two BCP systems were employed, a conventional poly(styrene-b-methyl methacrylate) (PS-b-PMMA) with relatively low χ and similar surface energies between blocks, and a high χ poly(styrene-b-methacrylic acid) (PS-b-PMAA) with distinct surface energies. The bottlebrushes, with either short side-chains of PS-r-PMMA or PS-r-PMAA random copolymers, were synthesized via ring-opening metathesis polymerization (ROMP). Remarkably, it was observed that the top and bottom interfaces of both BCP films were enriched with bottlebrush copolymers, regardless of the surface energy difference between blocks, hence, vertically oriented microdomains were achieved for both BCP systems. This can be attributed to the screening of polymer interactions by a good solvent during the spin-casting process, allowing architectural effects to play a role in surface segregation of bottlebrush copolymers, as confirmed by contact angle measurements and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). We believe that this concept can be further extended to various applications that require polymer films with functional surfaces.

Direct Photolithographic Patterning of Colloidal Quantum Dots Enabled by UV-Crosslinkable and Hole-Transporting Polymer Ligands.

Quantum dot (QD)-based displays call for nondestructive, high-throughput, and high-resolution patterning techniques with micrometer precision. In particular, self-emissive QD-based displays demand fine patterns of conductive QD films with uniform thickness at the nanometer scale. To meet these requirements, we functionalized QDs with photopatternable and semiconducting poly(vinyltriphenylamine-random-azidostyrene) (PTPA-N3-SH) ligands in which hole-transporting triphenylamine and UV-crosslinkable azide (-N3) groups are integrated. The hybridized QD films undergo chemical crosslinking upon UV irradiation without loss in the luminescence efficiency, enabling micrometer-scale QD patterns (pitch size down to ∼10 µm) via direct photolithography. In addition, the conjugated moieties in the ligands allow the crosslinked QD films to be used in electrically driven light-emitting diodes (LED). As the ultimate achievement, a patterned QD-LED was prepared with a maximum luminance of 11 720 cd m-2 and a maximum external quantum efficiency (EQE) of 6.25%. The present study offers a simple platform to fabricate conductive nanoparticle films with micrometer-scale patterns, and thus we anticipate that this system will expedite the realization of QD-based displays and will also be applicable to the manufacture of nanoparticles for other electronic devices.