ACS Applied Polymer Materials最新文献

The end-group chemistry of cis-1,4-polyisoprene (PI) chains is critical in governing the exceptional mechanical performance of Hevea natural rubber (NR). PI chains exhibit distinct terminal groups, classified into ω and α types. Experimental studies have identified two types of ω terminal ends and six α terminal ends (α1, ..., and α6). In this study, we investigate five polyisoprene melt systems, each with unique combinations of terminal groups: hydrogen (H), ω, ω′, α₅, and α₆. The ω end consists of a dimethyl-allyl group bonded to two trans-isoprene units, whereas the ω′ group consists of an alanine dipeptide (ADP) segment linked to a dimethyl-allyl and two trans-isoprene units. The α₅ and α₆ groups correspond to the ester and hydroxy terminal groups. The studied systems include hydrogen-terminated _HPI_H (PI₀); ester-terminated _ωPI_α5 (PI_V); hydroxy-terminated _ωPI_α6 (PI_VI); and dipeptide-terminated _ω′PI_α5,α6 (PI_V′,VI′). Using all-atom molecular dynamics simulations, we evaluated conformational properties, including the end-to-end distance, radius of gyration, Kuhn length, and dynamic (end-to-end vector autocorrelation, Rouse modes) properties. Intermolecular interactions were characterized using radial distribution functions and the corresponding potentials of mean force. Pronounced hydrogen bonding among ω′–ω′ and ω′–α groups leads to slower dynamics and the formation of stable clusters in _ω′PI_α5,α6 systems. These clusters act as physical junction points (PJPs) stabilized by β-sheet-like hydrogen-bond networks between dipeptide terminal ends. The stress–stress autocorrelation function, G(t), reveals a chain length-dependent slowdown in relaxation dynamics for (PI_0,V) systems, with slower relaxation observed at N = 96 (N is the number of monomer present in each chain) compared to N = 24. In contrast, (PI_V′,VI′) chains exhibit faster relaxation at N = 96, attributed to weakened end-group associations and the absence of large clusters that dominate the N = 24 systems. These findings demonstrate that β-sheet-like PJPs may be the key to the outstanding properties of NR.

Over the past decade, imine chemistry has emerged as a critical tool in the design of vitrimers – polymer networks featuring dynamic associative cross-links. Imine-based vitrimers offer significant utility for a variety of applications, ranging from recyclable thermosets to separations membranes. In this study, we examine how cross-linker nucleophilicity and diffusivity influence the static and dynamic properties of polystyrene (PS) vitrimers containing imine linkages. PS vitrimers were synthesized through imine condensation between a precursor polymer bearing pendent aldehyde groups and a series of small molecule diamine cross-linkers. The cross-linker set, comprising both aromatic and aliphatic diamines, spans a broad range of nucleophilicities (pK_a = 3.0 to 10.5) and diffusion coefficients. For static properties, cross-linkers with larger molar volumes lowered the glass transition temperature (T_g), while the plateau modulus remained largely unaffected by the diamine structure. For dynamic properties, the temperature dependence of fast segmental motions is correlated with T_g. The rheological activation energy exhibited a linear relationship with both the pK_a and diffusion activation energy, indicating that these factors jointly govern the temperature dependence of the slow relaxation regime. pK_a, however, primarily dictated the rate of slow relaxation, as confirmed by the creep and SAOS measurements. The cross-link exchange attempt time showed no direct correlation with either pK_a or diffusivity. Overall, this work demonstrates that cross-linker nucleophilicity and diffusion are key determinants of the structural and rheological behaviors of imine-based vitrimers.

High-temperature proton exchange membranes (HT-PEMs) play a significant role in high-temperature proton exchange membrane fuel cell (HT-PEMFC) applications. In this work, a series of fluorinated poly(imide-co-benzimidazole) (PFIBIx) copolymers were synthesized as potential HT-PEM materials. The introduction of benzimidazole groups into the backbone of the polymers significantly enhanced PA uptake and retention of the membranes via acid–base interactions, endowing the PFIBIx membranes with a proton conductivity of 60–82 mS cm^–1 at 160 °C. Meanwhile, the introduction of fluorinated groups effectively suppressed excessive membrane swelling due to their acid-phobic nature. The PFIBIx membranes also exhibited excellent mechanical properties and oxidation stability. Notably, the single fuel cell with PFIBI₄₀, despite having a relatively lower conductivity of 67 mS cm^–1 at 160 °C, delivered a maximum power density of 210 mW cm^–2. This enhanced performance is attributed to its superior stability and overall balanced properties, demonstrating that PFIBI₄₀ is a highly promising candidate for HT-PEM applications.

The chemical fixation of carbon dioxide (CO₂) into value-added chemicals is a pivotal research direction toward achieving carbon neutrality and sustainable chemistry. Herein, a biomass-derived poly(ionic liquid) (BPIL) was designed from renewable chitin and low-cost pyridinium. The as-prepared catalyst exhibits excellent performance in the cycloaddition of CO₂ with various epoxides under mild/solvent-free/cocatalyst-free conditions. Furthermore, the catalyst demonstrates remarkable stability and recyclability with no significant loss of activity over five consecutive cycles. More importantly, a combination of in situ FTIR experimental studies and density functional theory (DFT) calculations reveals a crucial synergistic effect between the hydroxyl groups on the biomass support, acting as hydrogen bond donors (HBDs), and the iodide anions. This synergy effectively activates the epoxide and significantly lowers the energy barrier of the rate-determining step. This work not only provides an efficient and green catalytic system for CO₂ valorization but also offers a strategy for the rational design of multifunctional catalysts from renewable biomass.

Bismaleimide (BMI) resin is characterized by a high degree of cross-linking. However, its application is limited due to inadequate toughness. In this research, a series of thermoplastic reactive poly(arylene ether sulfone) (rPES-PPIs) resins with different propenyl contents were designed and used to toughen the N,N′-(4,4’-diphenylmethane) bismaleimide (BDM)/diallyl bisphenol A (DABPA) system. The study systematically examined the thermal stability, impact resistance, flexural strength, and fracture surface characteristics of both the BDM/DABPA system and the rPES-PPIs/BDM/DABPA blends. The findings indicated that the blend containing 10 phr of rPES-PPIs achieved an unnotched impact strength of 21.23 kJ/m², which is a 220.21% increase compared to the unmodified system, while the flexural strength reached a maximum increase of 38.80% over the unmodified system. Dynamic mechanical analysis (DMA) also revealed an increase in the glass transition temperature (T_g) of the blends. Additionally, the system exhibited a relatively low curing activation energy of 18.25 kJ/mol, which facilitates the curing process. These results suggest that rPES-PPIs can greatly enhance the toughness of cured BMI resin without compromising thermal properties, and a related toughening mechanism is proposed.

Conventional radical-based UV-curable acrylic pressure-sensitive adhesives (PSAs) are severely limited by oxygen inhibition, leading to incomplete surface curing and polymerization shrinkage. To address these issues, we report a cationic photopolymerization strategy based on vinyl ether-functionalized polyurethanes for fabricating high-performance optically clear PSAs. A vinyl ether-terminated prepolymer (PUE-BDO) was synthesized by the chain extension of an isocyanate-terminated polyurethane with 1,4-butanediol, followed by end-capping with 4-hydroxybutyl vinyl ether (HBVE). A difunctional vinyl ether monomer (IP-VE) was prepared from HBVE and isophorone diisocyanate. By systematically adjusting the ratios of PUE-BDO, IP-VE, and triethylene glycol divinyl ether (DVE-3), we achieved precise control over the cross-linking network and viscoelastic properties of the materials. The resulting PSAs exhibited exceptional optical clarity, with 99% transmittance and <0.3% haze, alongside rapid strain recovery (<1 s) and a high creep-recovery ratio (∼90%) after 100 loading–unloading cycles at 20% strain. At an optimal composition (50 wt % prepolymer), the PSA demonstrated a 180° peel strength of 18.2 N/25 mm and a loop tack of 17.3 N/25 mm. This study presents a robust and tunable cationic photocuring platform for next-generation flexible display encapsulation that is free from oxygen inhibition and capable of meeting demanding optical and mechanical requirements.

Driven by the miniaturization and integration of electronic components, escalating thermal loads have necessitated the development of materials with high thermal conductivity. However, the direct incorporation of thermally conductive fillers (e.g., carbon nanotubes, CNTs) into polymer matrices often resulted in poor dispersion and interfacial compatibility, thereby limiting overall performance. In this study, a biobased polyimide (Bio-PI) was synthesized from 2,5-furandicarbonyl dichloride (FDCA-Cl₂), a biobased FDCA derivative. Carboxyl-functionalized CNTs (c-CNTs) were engineered via SiO₂ core–shell encapsulation and ODA modification to obtain surface-functionalized m-CNTs. During composite formation, in situ encapsulation of m-CNTs by the Bio-PI matrix generated self-assembled microcapsule architectures, enhancing filler dispersion and interfacial compatibility to establish stable thermal networks. At 30 wt % loading, PI/m-CNTs-30% achieved a thermal conductivity of 2.00 W/mK, representing an 11.76-fold enhancement over neat Bio-PI (0.17 W/mK). Concurrently, the SiO₂ shell maintained balanced dielectric properties (ε_r = 6.53, tan δ = 0.026 at 1 MHz) and electrical resistivity (7.95 × 10¹² Ω·cm). This composite demonstrates significant potential as a heat-dissipating material for electronic devices, particularly in advanced packaging requiring stringent dielectric and insulating performance. This work presents a methodology for fabricating high-performance renewable thermal management materials.

The development of small-diameter artificial blood vessels for the treatment of cardiovascular disease faces critical challenges, including mismatches in mechanical properties, poor cellular compatibility, and a high propensity for thrombosis. In this study, we fabricated polycaprolactone (PCL)-based small-diameter vascular scaffolds by melt electrospinning technology. By optimizing processing parameters, we successfully constructed a vascular framework with a hierarchical fibrous network. Biomimetic vascular scaffolds with three distinct architectures (star, triangle, and square) were systematically compared in terms of their performance. Further surface multifunctionalization was achieved using NaOH-induced hydrophilization, Ethyldimethylaminopropyl carbodiimide/N-hydroxy succinimide (EDC/NHS)-mediated heparin grafting, and coating with a rutin-loaded gelatin methacryloyl (GelMA) hydrogel. Analysis demonstrated that the optimized structure of stars met the mechanical requirements of human coronary arteries, exhibiting a fracture elongation of 929.8% and a Young’s modulus exceeding 1.5 MPa. The 0.1% rutin-loaded coating enabled sustained drug release with <6% mass loss over 6 days while maintaining high cell viability. Furthermore, heparinization significantly enhanced anticoagulant properties, with hemolysis rates <5%. Overall, we present an integrated “process-structure-function” strategy to successfully engineer small-diameter artificial blood vessels with favorable mechanical performance, biocompatibility, and in vitro anticoagulant properties, thereby providing a reliable material platform and technical route for the in-depth fundamental research and further developmental exploration of small-diameter vascular substitutes.

The high density and fragility of traditional silica glass limit its applications in some fields, such as distributed photovoltaic (PV), automobiles, or aerospace industries. Lightweight and transparent glass-imitation materials (GIMs) still face substantial challenges, especially regarding high modulus and surface scratching. In this study, we propose an interconnected polymer networks (ICN) structure of polyurethane (PU) phase and acrylate phase with adjacent bonding between them by employing a dual functional monomer hydroxypropyl acrylate (HPMA). Rheological, thermodynamic, mechanical, scanning electron microscopy (SEM) and hydrogen spectroscopic nuclear magnetic resonance (¹H NMR) results prove the adjacent bonding interconnected polymer networks (ab-ICN) structure. By optimizing the mass ratio of the two phases, the resulting synergistic effect of the ab-ICN systems results in GIMs with excellent transparency (up to 91%, thickness 2.7 mm), high-temperature resistance (glass transition temperature up to 147 °C), high strength (flexural strength up to 141 MPa), high modulus (flexural modulus up to 3894 MPa), low expansion (67.36 μm (m·°C)⁻¹) and scratch resistance. Furthermore, GIMs PV module shows analogous photoelectric conversion efficiencies to glass PV module with a 45.6% mass reduction, offering a promising lightweight avenue for developing PV and other applications.

The advancement of high-frequency communication technologies has necessitated the development of materials exhibiting low dielectric constants and minimal dielectric loss. Among various approaches, the most effective strategy for fabricating low-dielectric materials involves the incorporation of air into a polymer matrix. In this investigation, poly(aryl ether ketone) containing fluorenyl groups (PEK-F) was synthesized to produce high-performance foams characterized by inherent flame retardancy (OI ≥ 33.7%), high temperature resistance, an exceptionally low dielectric loss (D_f = 0.0003), and a dielectric constant (ε) of 1.07 at high frequency. The enhanced properties of the PEK-F foams are attributed to the rigid molecular chains of the PEK-F resin, which confer notable mechanical strength even at elevated temperatures of up to 180 °C. This thermal stability is critical for electronic components used in high-frequency communication systems that undergo high-temperature processing. Additionally, the PEK-F foams demonstrate excellent processability, as evidenced by their ability to be fabricated into flexible and transparent slices, a feature enabled by their uniform microcellular structure. These characteristics underscore the potential applicability of PEK-F foams in precision electronic components.