ACS Macro Letters最新文献

Inspired by the concept of multipotent stem cells, this research explores the use of tempering to program the mechanical properties of elastomeric dynamic covalent networks (DCNs) that contain thia-Michael bonds. These DCNs are composed of benzalcyanoacetate-based Michael acceptors and thiol-functionalized poly(ethylene glycol) (PEG) derivatives of varying molecular weights and architectures. The impacts of tempering on the thia-Michael adduct formation and dynamic reaction-induced phase separation (DRIPS) morphology were investigated by Raman spectroscopy and atomic force microscopy. Uniaxial tensile testing revealed that increasing the tempering temperature reduced the Young’s modulus and maximum stress while maintaining high elastic recovery and low energy dissipation as evidenced by cyclic loading–unloading experiments. The tempering process is completely reversible, and retempering the film at a different temperature allows the mechanical properties to be tuned. These findings establish a simple, reprogrammable strategy to access multipotent elastomers from a single feedstock through tempering of thia-Michael-based dynamic covalent networks.

Thermosets are indispensable for their lightweight and excellent thermomechanical properties but suffer from nonrecyclability, exacerbating plastic pollution. Covalent Adaptable Networks (CANs), leveraging dynamic covalent bonds, address this challenge. This study explores β-amino sulfonamides (BASA) as novel dynamic and thermoreversible linkers for CANs. Compared to previously investigated β-amino amides (BAAs), small molecule BASA studies show a faster amine exchange reaction via (retro)aza-Michael reactions in a temperature window from 140 to 180 °C. More importantly, in contrast to the acrylamide monomers released from BAAs, the vinyl sulfonamide monomers released from BASAs are more robust and can resist homopolymerization at elevated temperatures. We showed that bisfunctional vinyl sulfonamide cross-linkers enable the synthesis of CANs with tunable properties, as verified through thermomechanical and rheological analysis. The anticipated increased thermal stability of BASA-based CANs was shown by the retention of mechanical and rheological performance over at least five recycling cycles.

Advancing sustainable plastics is crucial to achieving a circular plastic economy. Baroplastics, block copolymers exhibiting order–disorder transitions under pressure, allow polymer processing at ambient temperatures, reducing energy use and avoiding thermal degradation. Their application, however, has been limited by structural constraints. This study introduces poly(ε-caproclactone-random-5-ethyleneketal ε-caprolactone)-block-poly(l-lactide) (PmCL-b-PLLA) as a “baroplasticizer” for nonbaroplastic PLLA. Blending with the block polymers lowered PLLA’s flow temperature by up to 100 °C (160 to 60 °C at 50 MPa) while preserving molecular weight after repeated pressure cycles, ensuring recyclability. The improved formability would arise from a pressure-induced ordered (solid)-to-disordered (melt/solid) phase transition. This work eliminates structural constraints in baroplastics, enabling broader low-temperature processing applications and advancing sustainable polymer technologies.

This study presents a scalable, solution-phase protocol for the synthesis of monodisperse oligoamides with nylon-4, nylon-6 and hybrid nylon-4/6 backbones, enabled by a group assisted purification strategy. For this, unnatural amino acid monomers are iteratively coupled onto a phosphonate-functional soluble support, yielding uniform oligomers bearing orthogonal functional end groups that allow their solid-state polycondensation (SSP). Pure monodisperse oligomer precursors of nylon-4 exhibits thermal limitations due to their low ceiling temperature, resulting in low molecular weight products after SSP. In contrast, incorporation of strategically positioned nylon-6 units effectively suppress backbiting and facilitates efficient SSP, producing well-defined nylon-4/6 copolymers. This unique design approach offers unprecedented control over the polyamide microstructure and establishes a versatile route toward polyamide synthesis with potential for customizing material properties.

Polyhydroxyalkanoates (PHAs) have served as promising alternatives to traditional petroleum-based plastics. Chemical synthesis of stereoregular PHAs via stereoselective copolymerization of racemic-epoxides with carbon monoxide (CO) has not yet been achieved. Here, the design of trimetallic ligand platform featuring various electronic nature and steric demand enables Cr^III-catalyzed stereoselective copolymerization of racemic-epoxides with CO, yielding 9 types of functionalized PHA products having 0.70 syndiotacticity. Kinetic study has revealed that trimetallic complex favored the intramolecular chain propagation for the preparation of high molecular weight PHAs with high reactivity and moderate syndiotacticity, while monometallic complex promoted the intermolecular chain propagation toward isotactic-enriched PHAs.

Smart fluorescence gels provide significant advantages in encryption, such as high storage, user-friendly operation, low cost, and enhanced security. Nevertheless, current fluorescent gels are predominantly limited to static or binary encoding, hindering their potential for high-level multistate encryption. Herein, the ligand (Tpy-Emim) based on terpyridine-vinyl imidazole salt was synthesized. Fluorescent ionogels (P(ACMO/BA/Tpy)-Ln) with robust mechanical properties, strong adhesion, and hydrophobicity were developed through a one-step in situ photopolymerization process. These ionogels exhibited multicolor fluorescence (red, orange, green, white) by adjusting the Eu³⁺/Tb³⁺ ratio. Importantly, the ionogel (P(ACMO/BA/Tpy)-Eu₄₀/Tb₄₀) showed excitation-dependent luminescence with colors changing under different excitation energies. Leveraging this property, a dynamic encryption system was developed, integrating 2D codes into 3D color codes. The 2D code was readable in natural light, while the 3D code required specific UV light to reveal the correct data. Additionally, the ionogel’s fluorescence quenched upon exposure to ammonia vapor, enabling decoding of the embedded 2D code. This study provides valuable insights for developing fluorescence ionogels for dynamic and controllable orthogonal information encryption.

Selective ion separations are central to technologies spanning water purification, resource recovery, and clean energy. Conventional polymer membranes, which rely on steric hindrance or Donnan exclusion, struggle to discriminate between chemically similar ions in high-ionic-strength environments. Ligand-functionalized membranes offer a transformative strategy by embedding molecular recognition directly into polymer matrices, enabling selective complexation and transport. This Viewpoint highlights the structure–function relationships underlying ligand-mediated ion separation, emphasizing the interplay of dehydration penalties, ligand coordination, and nanoscale confinement. We discuss design principles, denticity, donor identity, rigidity, and spatial organization, alongside the permeability–selectivity trade-off, multicomponent effects, and stability challenges. Finally, we outline emerging strategies, from bioinspired ligands to computationally guided design, that chart a path toward next-generation membranes for precise and energy-efficient ion separations.

Mechanoluminescent polymers capable of fluorescence modulation have attracted considerable interest for applications in stress-sensing and flexible electronics. Though Förster resonance energy transfer (FRET) has proven to be an effective mechanism for generating mechanoresponsive fluorescence changes, current systems predominantly depend on force-induced structural changes in chromophores. Herein, we report a mechanofluorochromic strategy exploiting force-modulated distance control between a FRET pair. A furan-maleimide Diels–Alder (DA) adduct covalently linked to pyrene (donor) and dansylamide (acceptor) was designed and incorporated at the midpoint of poly(methyl acrylate) (PMA) chains. Mechanical cleavage of the adduct spatially separates the FRET pair, effectively abolishing energy transfer and concurrently activating photoinduced electron transfer (PET). In acetonitrile, ultrasonication shifted the fluorescence from yellow to high-quality white light. Through changing the solvents, we demonstrate programmable multicolor switching. In toluene, the fluorescence evolves from green to cyan, while in DMF, rapid activation induced a transition from yellow to white emission. Each solvent system exhibits unique kinetic trajectories, enabling precise control over the chromatic response. This work demonstrates that controlled modulation of the FRET distance provides a versatile strategy for developing smart, multicolor mechanoluminescent materials without the need for a complex system design.

Solid polymer electrolytes (SPEs) possess several advantages over liquid electrolytes, such as stability and nonflammability, that can enable next-generation batteries with improved performance. However, current SPEs suffer from sluggish Li⁺ transport and poor mechanical properties. Polymeric ionic liquids (PILs) have emerged as promising electrolyte materials due to their ability to dissociate high concentrations of Li salts. High segmental motion enables fast ion transport, but it has been challenging to find materials that are both rubbery and also have high salt dissolution. We find improved transport properties and rheological behavior for a PIL with a flexible siloxane backbone (designated as PMS-ImTFSI) in the salt-in-polymer (<50 wt % salt) regime. PMS-ImTFSI exhibits a long-lived rubbery plateau in shear rheology at salt loadings up to ca. 20 wt % salt that imparts it with greater elasticity. At the same time, PMS-ImTFSI enables high Li⁺ conductivity (up to 2 × 10^–5 S/cm at 90 °C) due to beneficial ion–ion correlations. A transition from salt-in-polymer to polymer-in-salt regimes as seen consistently across rheology, NMR diffusometry, inverse Haven ratios, and X-ray scattering suggests that PILs with flexible, nonpolar backbones at low salt loading can form ion-rich domains that simultaneously exhibit high Li⁺ conductivity and robust mechanical properties. At high salt loading, the microstructure disappears, and the optimal properties are lost. These findings guide the design of advanced SPEs for next-generation batteries.