ACS Macro Letters最新文献

Vinyl ketone polymers, including poly(phenyl vinyl ketone) and poly(p-chlorophenyl vinyl ketone), were successfully synthesized under light using atom transfer radical polymerization (ATRP). This marks the first successful attempt at ATRP of vinyl ketones. The polymerization kinetics revealed chain growth and maintained livingness, as further evidenced by successful chain extension using ethyl acrylate. The efficient main-chain cleavability of the polymers was confirmed under UV light. While the attainment of low dispersity remains an enduring challenge, this work offers promising potential for future success.

Accurate thiol quantification is essential for advancing thiol–X-ligation strategies in polymer and materials synthesis. Conventional assays, most notably Ellman’s test, are limited in scope, particularly for hydrophobic or multifunctional thiols. Here, we introduce a straightforward and broadly applicable ³¹P NMR spectroscopy method for thiol quantification, using 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (TMDP) as a phosphitylation reagent. The approach extends established ³¹P NMR protocols for hydroxyl and carboxyl group analysis to thiols, offering high specificity and stability in readout. The method demonstrates applicability across a wide range of substrates, from small organic molecules to polymeric multi thiols with M_n up to 8000 g·mol^–1. Comparative validation against Ellman’s assay and ¹H NMR spectroscopy reveals superior selectivity and resolution of the TMDP-based ³¹P NMR protocol, particularly for technical-grade thiols, where conventional methods fail to distinguish degradation products. This study establishes the TMDP-enabled ³¹P NMR as a reliable, information-rich tool for thiol quantification, giving simultaneously insights on hydroxy and carboxyl functionality patterns.

Soft colloids play a vital role in modern life and provide insights into the physics of vitrification. Soft colloidal glasses exhibit significant variations in dynamic fragility─the sensitivity of relaxation dynamics to concentrations. While particle softness, including cross-linking density and charge, influences fragility, their complex interplay obscures the fundamental physics. This study conducts a systematic investigation of 16 uncharged polystyrene soft nanoparticles (SNPs) with independently controlled diameter and elasticity. The research quantifies relaxation time as a function of particle concentration, diameter, and cross-linking density using two fitting parameters. Through this analysis, fragility is determined and correlated to the elastic energy per particle (particle elasticity multiplied by volume). Particles below a threshold elastic energy (smaller or softer) would deform readily under thermal energy, exhibiting strong glass behavior. In contrast, larger or stiffer particles undergo fragile glass transitions through a cooperative relaxation. This investigation establishes a dynamic phase diagram that predicts fragility transitions, addresses existing contradictions, and presents design principles for colloidal suspensions.

Mechanical recycling of polypropylene (PP) causes chain scission during high-temperature, high-shear processing, resulting in lower molecular weight (MW) fragments, which contain fewer tie chains between crystalline lamellae. This change can lead to significantly reduced mechanical performance, making the use of post-consumer recycled PP in new materials particularly challenging, especially as recent government policies mandate the use of recycled content at increasing levels. Previous strategies in addressing these needs rely on chemically crosslinking or introducing additives, which can be time-consuming, cost-prohibitive at scale, and/or further complicate waste streams. In this work, we demonstrate a solvent immersion annealing method that swells PP blends containing high and low MW fractions, promoting their co-crystallization, which leads to significantly improved mechanical performance of the blended materials. Specifically, our results show an over 6-fold increase in extensibility of PP blends, effectively enabling their reuse and extended lifetime. This work presents an innovative and straightforward method to address the recycling challenges of low MW PP without the need for additives, potentially opening new avenues for future research in blend compatibilization for addressing plastic circularity challenges.

Depolymerization is a promising approach to reduce plastic waste by regenerating monomers from polymers, presenting a compelling solution to maintain a circular polymer economy. However, vinyl polymers with all-carbon backbones are especially difficult to depolymerize due to significant thermodynamic and kinetic barriers. Developments in reversible-deactivation radical polymerization and catalytic methods demonstrate how tuning polymer structure and reaction conditions can address these challenges. This Viewpoint revisits early studies on radical depolymerization and recent advances enabling monomer recovery at lower temperatures. Exciting current trends to utilize depolymerization as a strategy for tuning polymer material properties and upcycling waste polymer to high-value products are discussed. We outline key directions to make vinyl polymer depolymerization scalable, efficient, and economically viable.

The limited ability to recycle or upcycle many commodity polymers with all carbon backbones poses a significant challenge to polymer chemists and society as a whole. In this work, sterically hindered cyclopropenes (CPEs) are used to promote ring-opening cross metathesis reactions with alkene-containing polymers to upgrade the original materials into functional copolymers through a formal backbone editing process. This polymer backbone editing process was able to achieve high conversion of the CPEs (>90%) and maintain reasonable postediting molecular weights (>22 kDa). The method was applied to different CPEs and olefin-containing polymers, resulting in changes in the chemical and thermal properties of the resulting copolymer materials. This work advances avenues for polymer upcycling processes, offering new directions for repurposing widely used olefinic polymers.

Biosourced polymers and aqueous thermoresponsive polymers have both received broad attention, but the two attributes are rarely merged. Here, furfural-derived alcohol and carboxylic acid are transformed into tetrahydrofuran(THF)-bearing epoxides, tetrahydrofurfuryl glycidyl ether (F²GE) and glycidyl 2-tetrahydrofuroate, by reacting with epichlorohydrin. Ring-opening polymerization catalyzed by an organic Lewis pair occurs in a highly selective manner, producing THF-functionalized polyethers with controlled molar mass (5.6–22.7 kg mol^–1) and low dispersity (1.09–1.12). Nonbiosourced (tetrahydrofuran-3-yl)methyl glycidyl ether is also synthesized and polymerized for comparison. The polyethers exhibit high thermal stability, minimal cytotoxicity, and structure-dependent cloud point temperature (T_cp) in water with polyF²GE showing the highest T_cp (24.1–37.3 °C) at all concentrations (0.1–1.0 mg mL^–1). Alkali metal halides exhibit variable “salting-in/-out” effects, with T_cp increased by NaI, LiI, or LiBr and decreased by NaCl, NaBr, or KCl. Also interestingly, the THF functionalities allow polyF²GE to selectively adsorb Fe³⁺ (95.3%) from an aqueous solution containing other ions (Ni²⁺, Co²⁺, and Mn²⁺) above T_cp.

Reversible polymer gels are attractive materials as their dynamic cross-links impart properties such as self-healing, stress relaxation, and stimuli-responsiveness. A wide variety of chemistries have been explored to access such networks, among which boronic ester bonds stand out for their biocompatibility, selectivity, and tunable dynamics. Macromer functionalization is a well-established strategy for introducing boronic esters into networks, as the defined architecture of the macromer provides predictable network topologies with a direct link between dynamic cross-link chemistry and bulk properties, traits difficult to design into conventional polymeric materials. However, altering macromer chemistry can be time- and cost-intensive. Here we describe an alternative, modular strategy in which boronic esters are prebonded and coupled to commercial thiol-terminated poly(ethylene glycol) macromers via UV-initiated “click” chemistry. This route enables straightforward network synthesis and characterization, proceeds in high yield under modest UV light intensities, and avoids byproducts that complicate gel mechanics. The modular nature of this approach allows access to macromer-based networks with tunable mechanical and dynamic properties, without the need to synthesize new macromers. The resulting materials display hallmark dynamic mechanical properties and new capabilities, such as spatiotemporal control over macromer-based gel formation, highlighting prebonded cross-linkers as a versatile platform for constructing macromer-based dynamic networks.

Selective elimination of senescent cells (SnCs) through senolytic strategies can counteract the progression of age-related dysfunction, but achieving precise, broad-spectrum, and controllable senolysis remains challenging. Here, we report PG@FBC, a polymeric senotherapeutic that exploits senescence-associated β-galactosidase (SA-β-gal) to trigger supramolecular disassembly and controlled photosensitizer release, enabling photodynamic senolysis with real-time imaging. Briefly, PG@FBC is composed of an amphiphilic block copolymer, POEGMA-b-GMA (PG), synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization from hydrophilic POEGMA and SA-β-gal-cleavable hydrophobic β-GMA units. Subsequent coassembly of PG with FBC photosensitizer affords core–shell nanoparticles featuring a hydrophobic core and a hydrophilic shell, with preferential uptake by SnCs. Once localized within SnCs, overexpressed SA-β-gal cleaves the β-GMA units of PG@FBC, triggering disassembly and releasing FBC. The released FBC binds intracellular proteins to mitigate aggregation-caused quenching (ACQ), enhance solubility, and amplify ROS generation under NIR-irradiation, inducing senolysis with minimal off-target cytotoxicity. In addition, the intrinsic fluorescence of FBC provides real-time imaging capability, establishing PG@FBC as a precise theranostic platform for integrated monitoring and elimination of SnCs in senescence-associated pathologies.

Uptake of proteins and ampholytic solutes into polyelectrolyte brushes underlies some biological processes and also applications in sensing or biomedicine. Especially uptake on the “wrong” side of the isoelectric point (pI) remains puzzling, with charge regulation and solute patchiness proposed as possible mechanisms. Using a hierarchy of approximations, coarse-grained molecular simulations, self-consistent mean-field, and a simple phenomenological model, we investigated the uptake of model ampholytic solutes into polyanionic brushes across varying pH, salt concentrations, pK_a values, and peptide sequences. In a narrow pH range on the wrong side of pI, charge regulation enables uptake of the ampholytes by inducing charge inversion so that they become positively charged in the brush despite being negatively charged in the bulk. This charge inversion can be calculated from the pH difference between the brush and the bulk, which is related to the Donnan potential. It is strongest for ampholytes with small differences between acidic and basic pK_a values and decreases with increasing salt. Our phenomenological model reproduces the universal effect of charge regulation promoting ampholyte uptake into brushes but fails to be quantitative. The mean field model is close to explicit simulations for alternating sequences, but fails to describe the effect of charge patchiness, which is only captured by explicit simulations. Thus, our phenomenological framework offers a practical rule of thumb for estimating uptake from experimentally accessible parameters without sophisticated calculations. Deviations from this rule of thumb for complex ampholytes, such as proteins or peptides with patterned charge sequences, are captured only by explicit simulations.