ABSTRACT The molecular architecture (topology) of bottlebrush polymers, featuring densely grafted side chains along a polymeric backbone, leads to unique physical properties, enabling their use as functional materials including elastomers and pressure‐sensitive adhesives (PSAs). Bottlebrush polymers can form additive‐free PSAs due to their architecture, but most are crosslinked materials that include all‐carbon backbones, have thermally unstable disulfide bonds, or do not reach the high molar masses needed for bottlebrush PSAs. Here, we applied the alternating free‐radical copolymerization of sulfur dioxide (SO 2 ) and norbornene‐based macromonomers in a grafting‐through approach to make bottlebrush polymers with number‐average molar masses exceeding 1100 kg/mol and backbone degrees of polymerization exceeding 900. These first examples of poly(olefin sulfone) bottlebrush polymers incorporated polyacrylate, polymethacrylate, polystyrene, and poly(lactic acid) side chains, all attached to a poly(norbornene‐ alt ‐SO 2 ) backbone. Under mild alkaline conditions, these very high molecular weight bottlebrush polymers degraded considerably within 10 min and completely within 4 h. Finally, a bottlebrush polymer synthesized using this approach behaved as a PSA with a peel strength of ∼1200 N/m, substantially higher than non‐degradable PSAs in commercial tapes. In sum, this work offers a versatile approach to synthesize triggerable and degradable bottlebrush polymer adhesives enabling end‐of‐life disposal following their intended applications.

This document provides recommendations addressing the long-standing dilemma of the wide variety of terms that are used to describe the two common classes of polymerization mechanisms in the scientific literature, which includes chemistry and polymer science textbooks. It is an update of a 1994 IUPAC document on this topic and provides clarification and hierarchical structure regarding the basic classification and terminology describing polymerization reactions. The term step polymerization describes polymerizations in which growth occurs by reactions between monomer, oligomer, or polymer molecules of any length. We clearly denote here the two subclasses of step polymerization: additive step polymerization (synonym: polyaddition) and condensative step polymerization (synonym: polycondensation). The term chain polymerization describes polymerizations that proceed via a chain reaction with monomer molecules adding to active sites on polymer chains. Subclasses of chain polymerization include additive chain polymerization and condensative chain polymerization. The terms provide a logical and straightforward structure for describing the two common classes of polymerization mechanisms. Previously defined terms relevant to these two classes of polymerization reactions are also repli-cated in this Recommendation document.

A group of 29 poly(olefin sulfone) copolymers and terpolymers was synthesized by free radical polymerization. Terpolymers followed predictable behavior with higher proportions of cycloalkene content leading to increased glass transition temperatures.

Polyvinyl chloride (PVC) is a thermoplastic used ubiquitously in households and industry owing to its light weight, mechanical strength, durability, low cost and ultraviolet and fire resistance1,2. With a production volume of about 60 million tonnes annually2, post-consumer and post-industrial PVC waste pose marked environmental challenges, such as leaching chlorohydrocarbons and additives, which contaminate groundwater and soil1-4. To address the formidable challenge of recycling PVC and achieving carbon circularity, valorization into high-value products is essential to mitigate the associated costs and offer high financial incentives for reusing plastic waste5-14. Here we report a method for upcycling PVC into high-value lubricants with controllable viscosities. Using AlCl3 at a mild temperature of 70 °C, PVC undergoes dechlorination, alkylation and chain scission, producing vinyl-derived polyalphaolefins (vPAO). PVC serves as an effective template for the alkylation of α-olefins of various chain lengths, producing vPAO with limited short branches in the backbone without the need for metallocene catalysts essential to current PAO technology. The PVC-derived lubricants exhibit tunable molar masses, kinematic viscosities at 100 °C (KV100 ≈ 14.9-26.3 centistokes), a low coefficient of friction (COF ≈ 0.08-0.15) and a high viscosity index (VI up to 130). This work highlights an economical approach to using PVC as a low-cost feedstock to synthesize high-value lubricants with superior tribological properties, meeting the demand for sustainability in both the plastic and lubricant industries.

The correct use of IUPAC terminology can facilitate clarity in scientific publications, litigation, and education. This document summarizes IUPAC's recommendations for polymer terminology. In the version attached in the Supplementary Information, hyperlinks lead to the original source material, and screen-tips give the definitions as published by IUPAC.

The self-assembly of amphiphilic bottlebrush block copolymers (BCPs), featuring backbones densely grafted with two types of side chains, is less well understood compared to linear BCPs. In particular, the solution self-assembly of tapered bottlebrush BCPs-cone-shaped BCPs with hydrophilic or hydrophobic tips-remains unexplored. This study investigates eight tapered and four cylindrical bottlebrush BCPs with varied ratios of hydrophobic polystyrene (PS) and hydrophilic poly(acrylic acid) (PAA) side chains, synthesized via sequential addition of macromonomers using ring-opening metathesis polymerization (SAM-ROMP). Self-assembled nanostructures formed in water were analyzed using cryogenic transmission electron microscopy, small-angle neutron scattering, and dynamic light scattering. Most BCPs generated multiple nanostructures with surface protrusions, including spherical micelles, cylindrical micelles, and vesicles, alongside transitional forms like ellipsoids and semi-vesicles. Coarse-grained molecular dynamics simulations supported the experimental findings, which revealed two distinct self-assembly pathways. The first involved micelle fusion, producing elliptical and cylindrical aggregates, sometimes forming Y-junctions. The second pathway featured micelle maturation into semivesicles, which developed into vesicles or large compound vesicles. This work provides the first experimental evidence of vesicle formation via semivesicles in bottlebrush BCPs and demonstrates the significant influence of cone directionality on self-assembly behavior in these cone-shaped polymeric amphiphiles.

There has been growing interest in polymeric systems that break down or undergo property changes in response to stimuli. Such polymers can play important roles in biological systems, where they can be used to control the release of therapeutics, modulate imaging signals, actuate movement, or direct the growth of cells. In this Perspective, after discussing the most important stimuli relevant to biological applications, we will present a selection of recent exciting developments. The growing importance of stimuli-responsive polysaccharides will be discussed, followed by a variety of stimuli-responsive polymeric systems for the delivery of small molecule drugs and nucleic acids. Switchable polymers for the emerging area of therapeutic response measurement in theranostics will be described. Then, the diverse functions that can be achieved using hydrogels cross-linked covalently, as well as by various dynamic approaches will be presented. Finally, we will discuss some of the challenges and future perspectives for the field.

Combining polysaccharides with polypeptides enables growth of diverse nanostructures with minimal toxicity, low immune response, and potential biodegradability. However, examples of nanostructures combining polysaccharides with polypeptides are limited due to synthetic difficulties and related issues of solubility, purification, and characterization, with previous reports of polysaccharide-block-polypeptide block copolymers requiring methods such as polymer-polymer coupling and post-polymerization modifications paired with difficult purification steps. Here, we synthesized dextran-block-poly(benzyl glutamate) block copolymers in water via polymerization-induced self-assembly (PISA) to form nanostructures in situ, studying their morphologies using experimental methods and molecular modeling. Transmission electron microscopy revealed globular but non-spherical nanostructures throughout the PISA process, in contrast to PISA processes using poly(ethylene glycol) (PEG) as the hydrophilic block, which have shown a range of well-defined nanostructures. Coarse-grained molecular dynamics simulations on several homopolymers and block copolymers revealed that dextran chains interacted more strongly with each other compared to PEG, and that water packed less densely around dextran than around PEG. The combined experimental and computational results indicated that while dextran is hydrophilic, its interactions with itself led to the formation of unexpected nanostructures in this dextran-block-polypeptide system, suggesting that these interactions may be exploited to form unique nanostructures compared with other common hydrophilic blocks.

Polysaccharide graft (co)polymers represent a fascinating, complex, and diverse class of materials. By combining the sustainable, biodegradable, and abundant nature of polysaccharides with the physicochemical tunability of synthetic polymers, polysaccharide graft (co)polymers are appealing candidates for high-performance sustainable materials. Careful synthetic design of polysaccharide graft (co)polymers, while challenging, is necessary to fully understand their structure, which is required to elucidate structure-property relationships. With explorations including stimuli responsive nanoparticles, renewable thermoplastic elastomers, and smart drug delivery systems, polysaccharide graft (co)polymers show great promise in a variety of applications. In this review, we discuss the synthetic tools available in producing well-defined polysaccharide graft (co)polymers, as well as their applications and structure-property relationships, highlighting the value of these materials to those striving for a sustainable future.

Self-assembled peptide-H2S donor conjugates (PHDCs) can deliver hydrogen sulfide in vitro and in vivo, yet the link between the supramolecular nanostructure morphology and cellular uptake remains unclear. Herein, we designed constitutionally isomeric PHDCs that self-assembled in aqueous solution into either nanoribbons, nanofibers, or nanobelts with various dimensions based on cryogenic transmission electron microscopy and small-angle X-ray scattering. Nile-red loaded PHDCs showed morphology-dependent uptake by H9C2 cells based on fluorescence microscopy combined with flow cytometry and confocal imaging, where narrow, helically twisted nanoribbons entered most efficiently. All PHDCs released H2S at similar rates, but the amount of H2S released inside the cells depended on the internalization ability of each PHDC. Consistent with these results, the narrow twisted nanoribbons afforded the greatest protection against H2O2-induced oxidative stress. Overall, this study highlights how subtle molecular-level changes can influence nanostructure formation in supramolecular assemblies and ultimately affect their cellular uptake and biological activities.

Additive manufacturing (AM) is widely used in the medical, automotive, and prototyping industries due to its ability to print complex geometries. Multiple AM modes employ photopolymerization to fabricate an array of cross-linked polymer networks. Here, we use ring-opening metathesis polymerization to synthesize hydroxyl-terminated polybutadiene (HTPB) with control over molecular weight and hydroxyl functionality, while maintaining low dispersity. We then modified these HTPB samples to produce acrylate-terminated polybutadiene (ATPB), which combines the photocurable characteristics of acrylates with the material flexibility and elasticity of the polybutadiene backbone. Using a library of ATPB oligomers with systematic variations in molecular weight (M n = 3-11 kg/mol) and acrylate functionality (f = 3-20), we identified key structural parameters that modulate the glass-transition temperature (T g) and cure kinetics. The ATPB oligomers were then incorporated into photopolymerizable resin formulations and evaluated for cure kinetics, thermomechanical properties, and the ability to be printed into multilayer, complex structures with suitable resolution. Due to its fast cure rate and low T g, ATPB with functionality 4 and M n of similar to 9 kg/mol was selected for further study. This formulation enabled successful 3D-printing via UV-assisted direct ink write (DIW) of complex geometries, with fumed silica added to improve print fidelity. Mechanical testing revealed isotropic behavior in the XY plane and demonstrated that the material's compliant, rubbery properties are suitable in 3D-printed elastomeric applications.

Parkinson's disease (PD) is a chronic, debilitating neurodegenerative disorder marked by the progressive and irreversible loss of dopaminergic (DA) neurons in the nigrostriatal pathway. Although the precise mechanisms underlying PD remain unclear, extensive research suggests that chronic neuroinflammation plays a significant role in its pathogenesis. Recently, growing evidence has pointed to NOSH-aspirin, an aspirin derivative that releases both nitric oxide (NO) and hydrogen sulfide (H2S), as a potent anti-inflammatory agent. However, its neuroprotective properties remain underexplored. This study assessed the protective effects of NOSH-aspirin against 6-hydroxy dopamine (6-OHDA)-induced neurotoxicity in a PD-like animal model. To induce the model, 6-OHDA (20μg/rat) was injected into the right medial forebrain bundle (MFB) of male Wistar rats (N = 7/8 per group). After 24 h, daily oral treatment with NOSH-aspirin (25 or 100 mg/kg), or aspirin (38 or 100 mg/kg), began. Included were also a sham/vehicle control group and NOSH-aspirin (100 mg/kg) starting 3 days post-6-OHDA. On the 12th day, motor function was evaluated using behavioral tests, including the rotarod treadmill, beam walking test, open field, and apomorphine-induced rotations. Animals were then sacrificed for histological and molecular analyses, including immunohistochemistry (IHC) staining and Western blotting. Results show that, NOSH-aspirin particularly at a dose of 100 mg/kg, significantly improved motor impairments and provided neuroprotection to tyrosine hydroxylase-positive (TH+) neurons. These protective effects were associated with a reduction in the phosphorylation of MAPK family proteins: JNK, p38, and ERK. In conclusion, NOSH-aspirin but not aspirin exhibits potential as a therapeutic candidate for managing neuroinflammation-related neurodegenerative disorders, including PD.

Therapeutical application of hydrogen sulfide (H2S) is limited due to the lack of delivery routes for specific organs and the rapid and wide dispersal of H2S in vivo. While H2S shows adipogenic effects in vitro, its in vivo impacts on obesity remain unclear. This study applies a H2S-slow-releasing hydrogel (H2S gel) to deliver H2S locally in subcutaneous adipose tissue and examines local lipid accumulation in mice. H2S is released from H2S gels within 6 h and lasts for 72 h, elevating H2S levels in local adipose tissue but not in the plasma. Localized H2S gel delivery causes significant lipid accumulation and larger lipid droplet diameter in mouse adipose tissues. The expressions of sterol regulatory element-binding protein, peroxisome proliferator-activated receptor-γ, adiponectin, and perilipin are all upregulated by H2S gel injections. Local delivery and retention of H2S in adipose tissues increase lipid accumulation more in wild-type than in cystathionine-γ-lyase knockout mice. This study confirms the feasibility of selectively delivering H2S via injectable hydrogels and their effectiveness in regulating targeted tissue functions. Furthermore, this work deepens our understanding of the role of H2S in obesity development under physiological conditions and offers a practical implementation strategy for H2S-based therapeutic interventions.

Leptomeningeal collaterals are distal pial arterial anastomotic vessels that provide an alternative route for redistributing cerebral blood flow following arterial obstruction, thereby limiting tissue damage. However, the regulatory mechanisms and strategies to enhance this adaptive response remain under investigation. This study explored the pharmacological effects of Tie2 receptor activation, using the peptide agonist Vasculotide, following permanent middle cerebral artery occlusion (pMCAO). Vasculotide improved collateral growth and remodeling, which correlated with reduced infarct volume, enhanced blood flow, and functional recovery within 24hrs post-pMCAO. In contrast, collateral growth was attenuated in Tie2 and EphA4/Tie2 double knockdown mice, while the loss of EphA4 increased Tie2 and Ang-1 expression and mimicked the positive effects of Vasculotide following stroke. Furthermore, bulk RNA sequencing of meningeal tissue identified key transcriptomic changes, including alterations in AJ-associated transcripts, such as Krt5 , Krt14 , and Col17a1 , in the ipsilateral meninges of both endothelial cell-specific EphA4 knockout and Vasculotide-treated mice. Krt5 expression was found upregulated on meningeal arterial vascular network in injured KO mice, highlighting a potential new mediator of meningeal vascular remodeling. These findings illustrate that EphA4 and Tie2 play opposing roles in collateral remodeling, including the regulation of Krt5. Modulating their activity could potentially enhance the collateral response to stroke.

Persulfides (RSSH) and hydrogen sulfide (H2S) are endogenously produced bioactive molecules that serve important roles in vasculogenesis and tissue repair processes. Through the physical incorporation of RSSH/H2S donors into electrospun fibers, we designed polymeric fiber mats that released provasculogenic and cytoprotective reactive sulfur species over biologically relevant time scales. The release of small molecules from the fiber mats showed that 20-50% of the analytes were released from the scaffolds after 4 h. Tube formation assays indicated that the persulfide donors improved tube formation in human microvascular endothelial cells (HMVECs) over baseline levels under oxidative conditions (H2O2). Analysis of HMVECs on the electrospun fiber mats demonstrated cell viability >80% for all groups tested. This design enables controlled release of small-molecule prodrugs as a novel method toward the formation of tissue engineering constructs that deliver reactive sulfur species, including RSSH, addressing an ongoing challenge in the field of tissue engineering.

Leptomeningeal collateral vessels help redistribute cerebral blood flow following arterial obstruction, reducing tissue damage. This study investigates the Tie2 receptor peptide agonist Vasculotide in a permanent middle cerebral artery occlusion (pMCAO) model. Vasculotide enhanced early diameter enlargement of pre-existing pial collaterals, which may be mediated by structural remodeling, as evidenced by endothelial proliferation. These changes correlated with reduced infarct volume, blood-brain barrier disruption, enhanced blood flow, and functional recovery at 3-28 days post-pMCAO. Conditional endothelial cell (EC)-specific EphA4 knockout (KO) mice exhibited increased Tie2 and Ang-1 expression, mimicking the effects of Vasculotide on collateral size. Simultaneous genetic loss of EC-specific EphA4 and Tie2 attenuated these outcomes. Nitric oxide inhibition partially blocked collateral enlargement in EC-KO mice, suggesting the presence of additional contributors. Bulk RNAseq of meningeal tissue revealed upregulation of Krt5, Krt14, and Col17a1 in the ipsilateral meninges of Vasculotide-treated and EC-specific EphA4 KO mice. Notably, the number of Krt5-expressing cells is increased on the leptomeningeal arterial vasculature of KO mice, suggesting a novel contribution to collateral enlargement. The opposing roles of EphA4 and Tie2 in collateral dynamics are demonstrated, and a novel molecular program is identified that can be targeted to enhance their diameter enlargement in ischemic stroke.

Self-assembly of amphiphilic bottlebrush block copolymers (BCPs), which have backbones with two types of densely grafted side chains, is less well understood compared to their linear counterparts. Specifically, the solution self-assembly of tapered bottlebrush BCPs, which are approximately cone-shaped with specific cone directionality (hydrophilic or hydrophobic tips), remains unexplored. This work describes a series of 8 tapered and 4 cylindrical bottlebrush BCPs with varying ratios of hydrophobic polystyrene (PS) and hydrophilic poly(acrylic acid) (PAA) side chains, synthesized by the sequential addition of macromonomers ring-opening metathesis polymerization (SAM-ROMP) method. The nanostructures formed by these BCPs in water were evaluated using cryogenic transmission electron microscopy, small-angle neutron scattering, and dynamic light scattering. Results showed that most BCPs formed multiple types of nanostructures, all with surface protrusions, including spherical micelles, cylindrical micelles, and vesicles, with transitional structures between each, such as ellipsoids and semi-vesicles. Coarse-grained molecular dynamics simulations aided interpretation of the experimental data. Collectively, results revealed two distinct self-assembly pathways through which the BCPs evolved from micelles into complex nanostructures. One pathway involved micelle fusion, resulting in elliptical and cylindrical aggregates that in some cases fused further to form Y-junctions. The second pathway entailed micelle maturation into semivesicles, which subsequently formed vesicles and, at times, large compound vesicles. This study provides the first experimental evidence supporting vesicle formation via semivesicles in bottlebrush BCPs. Collectively, these findings highlight how structural parameters such as cone directionality influence self-assembly in these large, cone-shaped polymeric amphiphiles.

In an effort to synthesize chemically recyclable thermoplastic elastomers, a redox-switchable catalytic system was developed to synthesize triblock copolymers containing stiff poly(lactic acid) (PLA) end blocks and a flexible poly(tetrahydrofuran- co- cyclohexene oxide) (poly(THF- co -CHO) copolymer as the mid-block. The orthogonal reactivity induced by changing the oxidation state of the iron-based catalyst enabled the synthesis of the triblock copolymers in a single reaction flask from a mixture of monomers. The triblock copolymers demonstrated improved flexibility compared to poly( l -lactic acid) (PLLA) and thermomechanical properties that resemble thermoplastic elastomers, including a rubbery plateau in the range of −60 to 40 °C. The triblock copolymers containing a higher percentage of THF versus CHO were more flexible, and a blend of triblock copolymers containing PLLA and poly( d -lactic acid) (PDLA) end-blocks resulted in a stereocomplex that further increased polymer flexibility. Besides the low cost of lactide and THF, the sustainability of this new class of triblock copolymers was also supported by their depolymerization, which was achieved by exposing the copolymers sequentially to FeCl 3 and ZnCl 2 /PEG under reactive distillation conditions.