ACS Macro Letters最新文献

Blends of charged and neutral polymers are of interest due to potential applications in rechargeable batteries. In this study, concentration fluctuations in blends of charged poly[lithium 3-(methacryloyloxy)propylsulfonyl-1-(trifluoromethanesulfonyl)imide] (PLiMTFSI) and neutral poly(ethylene oxide) (PEO) were investigated by small-angle neutron scattering (SANS). The scattering data were analyzed in the framework of the random phase approximation (RPA). Since ion dissociation can lead to stiffening, the charged polymers were approximated as rods, while the neutral polymers were assumed to be random coils. This approach works reasonably well at low weight fractions of charged polymers. For blends with higher weight fractions of the charged polymer, concentration fluctuations were highly suppressed, resulting in q-independent coherent structure factors that are inconsistent with the rod–coil RPA.

Lignin-based nonisocyanate polyurethanes (NIPUs) with tunable properties and photomodifiable capability were prepared through polyaddition of diamines and lignin-based bis-cyclic carbonates bearing α,β-unsaturated ketone. These bis-cyclic carbonates were synthesized from lignin-based phenols via Aldol condensation, O-glycidylation and cycloaddition of CO₂. Model reaction of vanillin-based cyclic carbonate (BVKCC) and n-hexylamine confirmed efficient aminolysis of cyclic carbonate and partial aza-Michael addition of α,β-unsaturated ketones at ambient temperature. Significantly, this aza-Michael adduct reverted quantitatively to the original α,β-unsaturated ketone upon heating to 100 °C. Aminolysis kinetics of BVKCC and n-hexylamine was investigated by ¹H NMR and DFT calculation. TGA, DSC and tensile tests revealed that these NIPUs exhibited excellent thermal and mechanical properties with T_d5%, T_g and tensile strength reaching up to 318 °C, 60.2 °C and 44.5 MPa, respectively. Crucially, the retained α,β-unsaturated ketone enables facile postpolymerization modification via UV-triggered [2 + 2] cycloaddition, leading to a significant enhancement of thermal properties.

Highly scattering materials have widespread applications in daily life. Achieving efficient light scattering often requires the use of high-refractive-index inorganic materials, such as titanium dioxide. However, the production of titanium dioxide particles leads to serious environmental pollution, and since 2020, they have been classified by the EU as a Category 2 carcinogen for inhalation. Therefore, it is urgent to develop safer materials for preparing highly scattering products, such as polymers. Recently, scientists have made remarkable progress in the preparations and applications of highly scattering polymeric materials through mimicking the delicate internal structure of white-appearing creatures found in nature. This viewpoint summarizes the current progress and applications in highly scattering polymeric materials and forecasts future trends. Unlike previous reviews, this work systematically evaluates the use of natural polymers─specifically cellulose and its derivatives─for producing highly scattering materials and their corresponding applications in optoelectronics, wearable devices and passive radiative cooling.

Graft block copolymers have the potential to serve as universal compatibilizers for immiscible polymer blends, but their engineering is impeded by the lack of a theoretical framework explaining how the enhanced interfacial adhesion of the compatibilized system is impacted by molecular architecture. We address this problem via coarse-grained molecular dynamics simulations of the uniaxial elongation of a ternary system of AB graft copolymers adsorbed at an immiscible, glassy, A/B homopolymer interface. The resulting toughness data are explained by a model for the removal of interfacial crossings that reflects the more facile reptation of grafts relative to the trapped entanglements that constrain the backbone. The model predicts that the toughness should be approximately linear with respect to the geometric mean of total backbone and graft entanglements prior to elongation, consistent with the molecular dynamics simulations and thus providing a direct connection between the macroscopically observable toughness and the microscopic entanglement network.

This study demonstrates a strategy to control lattice symmetry in a polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer hybridized with a small fraction of NH₂-tethered Fe₃O₄ magnetic nanoparticles incorporated within the cylindrical PMMA microdomains. A low-intensity magnetic field (= 350 mT) was applied following large-amplitude oscillatory shear alignment, transforming the shear-aligned hexagonally packed cylinders (HEX) into centered rectangular cylinders (CR) stabilized through microdomain reorientation that relieved chain crowding and stretching of the PS blocks. In contrast, applying the magnetic field to unoriented HEX induced reorganization into lamellae aligned parallel to the field. The lamellar phase represented the thermodynamic equilibrium state, whereas the CR phase was a kinetically stabilized metastable structure governed by the prealigned framework. These findings highlight low-intensity magnetic manipulation as an effective “noncontact tweezer” for tuning lattice symmetry in block copolymers via the interplay of magnetic anisotropy and initial microdomain orientation.

Shape-memory effects and mechanochromic properties in soft materials have attracted significant attention due to their potential applications in biomedical engineering. Herein, we use a simple strategy to integrate these two properties into a single biocomposite material, which is achieved by embedding cellulose nanocrystals (CNCs) into the keratin matrix (which is intrinsically shape morphable). Via the evaporation-induced self-assembly process, CNCs self-organize into a chiral nematic crystal structure with a specific pitch and are stabilized within the keratin matrix by hydrogen bonds. The physical cross-linking effect of CNCs significantly improves extensibility, tensile strength, and shape-memory recovery. During the deformation of keratin composite films, structure color variation from dark black to bright blue is observed, resulting from the variation of the CNC helical pitch that selectively reflects different wavelengths of polarized light to exhibit iridescence. This work presents dual-functional biocomposites in an eco-friendly method, which can be used as high-strain optical sensors.

Stimuli-responsive polymer brushes enable the selective capture and release of oil droplets from an aqueous phase. We study pH-switchable poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) grafts on weakly and strongly oleophilic surfaces. Under basic conditions, PDMAEMA is neutral and collapses, absorbing oil; under acidic conditions, it becomes polycationic, extends, and expels the droplet. On a weakly oleophilic substrate, this mechanism releases 86% of the oil, but on a strongly oleophilic substrate, only 0.5% is expelled due to the substrate’s strong attraction. To overcome this, we design a block copolymer brush with a PDMAEMA top layer above a pH-insensitive, permanently cationic, water-swollen poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) (PMETAC) cushion that blocks oil access to the substrate. Upon acidification, this architecture releases 99% of the oil, even from strongly oleophilic surfaces. Furthermore, although low grafting density compromises switchability for the homopolymer, the block brush retains efficient catch-and-release performance.

Fiber-reinforced polymer composites (FRPCs) are widely used in aerospace and lightweight automotive materials, and renewable energy due to their exceptional strength-to-weight ratio. Epoxy resins, the most common matrices in FRPCs, offer excellent mechanical performance but suffer from two major drawbacks: their thermoset nature makes composites unrecyclable, preventing fiber recovery, and their petroleum-derived origin raises environmental and sustainability concerns. In this work, we developed a biobased epoxy resin which incorporated dynamic covalent bonds, synthesized from l-malic acid and sorbitol polyglycidyl ether, and applied it to the fabrication of FRPCs. The resulting resin and its composites exhibited outstanding mechanical performance, comparable to or even surpassing those of conventional petroleum-based systems. More importantly, the reinforcing fibers (carbon and basalt fibers) were fully recovered through a solution-based process and reused to fabricate next-generation FRPCs without loss in mechanical performance. Furthermore, the recovered resin solution could be directly reused for photocuring-based 3D printing without additional purification or separation steps.

The development of recyclable thermoplastic materials derived from natural sources is crucial in addressing the global plastic pollution problem. Herein, we used natural cellulose as a raw material to prepare a series of cellulose thermoplastics that are easy to recycle and have adjustable properties and excellent toughness through a homogeneous etherification process. The introduction of ether groups significantly weakens the hydrogen bonding interactions between cellulose chains, thereby facilitating the thermal motion of these chains. By changing the chemical structure and amount of ether groups, the glass transition temperature of cellulose ethers can be adjusted in the range 95–173 °C, and thermoplastic processing can be realized at 180–250 °C. The tensile strength of the obtained cellulose thermoplastics can be adjusted in the range 5–60 MPa, and the elongation at break can be adjusted in the range 15%–70%, which is much higher than the toughness of the reported cellulose thermoplastic materials and meets the performance requirements of common plastics. Moreover, they have an excellent water resistance. Even after long-term immersion in a high-humidity environment and water, the tensile strength remains basically unchanged and the toughness is slightly improved. Cellulose thermoplastics can be processed into various plastic forms such as water cups, straws, packaging materials, and fibers through common thermoplastic processing methods. Such high-performance thermoplastics based on natural polymers are expected to be a promising candidate for sustainable plastic.

It is known that reversible–deactivation radical polymerization (RDRP) offers distinct advantages in preparing homogeneous gel network microstructures. However, flexibly regulating hydrogel network microstructures via RDRP remains a significant challenge. Herein, we fully leveraged the advantages of atom transfer radical polymerization (ATRP) in preparing well-defined polymers and uniform hydrogel networks and proposed a strategy to construct hydrogel structures with a controlled hierarchical network. This approach employs a presynthesized, well-defined telechelic bromide macroinitiator (via ATRP) to initiate the photoATRP of vinyl monomers and divinyl cross-linkers. A primary polymer network was first formed by the telechelic macroinitiator. Subsequently, the active chain-end sites initiated ATRP of small-molecule cross-linkers, thereby grafting a covalently linked secondary cross-linked network. In other words, we have embedded larger, uniformly sized pores within a smaller, homogeneous network structure. The size of these “macropores” can be tuned by adjusting the molecular weight of the macroinitiator. This hierarchical architecture endows the hydrogel with significantly altered swelling behavior and mechanical properties. Furthermore, by using carbon-dot-catalyzed aqueous photoATRP, this type of hydrogel with a controllable hierarchical structure can be fabricated via digital light processing (DLP) 3D printing technology. This work provides new insights into the regulation of the microstructure and macroscopic properties of hydrogel materials.