ACS Applied Polymer Materials最新文献

Recently, cloud computing and high-density data centershave intensifiedthermal management and fire safety challenges, creating a need formultifunctional EP composites with reliable thermal, electrical, mechanical,and flame-retardant performance. Inspired by the hierarchical fiberstructure and strong interfacial interactions of natural bamboo, thiswork first synthesized poly(ether ether ketone) and functionalizedits surface by depositing silica via plasma-enhanced chemical vapordeposition, followed by blending with flame-retardant fillers andincorporation into the epoxy system. The obtained composite achievesa limiting oxygen index of 43.7% and a thermal conductivity of 0.312W·m^–1·K^–1, representinga 57% increase over pure EP. At 80 °C, the breakdown field strengthof the composite still reaches 44.9 kV/mm, while the tensile and flexuralstrengths remain at 70 and 120 MPa, respectively, demonstrating excellenthigh-temperature stability. Combined thermogravimetric-infrared andcone calorimeter analyses indicate that this composite system reducesheat and smoke release, promotes the formation of a continuous, dense,and stable char layer, and thereby achieves synergistic flame-retardanteffects through the combined effects of condensed-phase protectionand gas-phase combustion suppression. These findings provide a usefulbasis for designing highly reliable epoxy composites for high-powerelectronic and electrical applications.

Cross-linkablespirobisindane-based polyimides were synthesizedand investigated as low-dielectric materials for high-frequency applications.The polymer composition was controlled by varying the molar ratioof diamines, and allyl groups were introduced through postpolymerizationfunctionalization to enable subsequent thermal cross-linking. Thesuccessful introduction and cross-linking of the allyl groups wereconfirmed by ¹H NMR and FT-IR spectroscopy, together withgel fraction measurements. The resulting films were readily fabricatedby solution-based bar coating and exhibited enhanced hydrophobicityand thermal stability after cross-linking. Positron annihilation lifetimespectroscopy (PALS) revealed a composition-dependent reorganizationof the local free-volume structure upon cross-linking, rather thana uniform increase in free volume. In particular, the 55 series exhibiteda pronounced decrease in fractional free volume after cross-linking,whereas the 73 series showed relatively minor changes. Despite thesedifferent free-volume responses, the cross-linked X-BMDA films exhibitedimproved dielectric properties compared with their uncross-linkedcounterparts, indicating that the dielectric enhancement cannot beattributed solely to an increase in free volume. X-BMDA-55 exhibitedthe lowest dielectric constant (D_k = 2.20at 28 GHz) and dissipation factor (D_f =0.0063 at 10 GHz). These results demonstrate that the combinationof spirobisindane-based molecular design and post-cross-linking providesan effective strategy for controlling local molecular structure andachieving low dielectric properties in polyimide films.

Reverse-modepolymer-stabilized liquid crystal (RPSLC) smart windowsexhibit voltage off transparency and voltage on scattering, whichare well aligned with the requirements of daylighting and solar heatinsulation in buildings. These characteristics make RPSLC smart windowspromising energy-saving light-modulating devices for building applications.Existing RPSLC devices suffer from uneven interfacial alignment, themutual restriction between electro-optical properties, and poor cyclicstability. To address these problems, this work carries out an integratedcollaborative optimization from three dimensions of interface, polymercomponents, and microstructure. A self-assembled monolayer (SAM) isconstructed using a mixed system of octadecyl phosphate and bis(2-(methacryloyloxy)ethyl)phosphate. The resulting SAM enables uniform vertical alignment ofthe liquid crystals and strengthens interfacial coupling stabilitythrough chemical bonding. Flexible polyurethane acrylate is then introducedto optimize the internal polymer network structure and alleviate thetrade-off in the electro-optical performance of the devices. In addition,a two-step exposure method is used to construct periodic polymer-wallmicrostructures and enhance the electro-optical properties and cyclicstability of the devices. The experimental results show that the saturationvoltage of the prepared reverse-mode polymer-wall stabilized liquidcrystal smart windows is only 7.2 V, the contrast ratio can reach178, and they simultaneously possess excellent long-term cyclic stability.This strategy provides useful guidance for the design of RPSLC smartwindows with improved electro-optical performance and cyclic stabilityfor building-related applications.

Designing stimuli-responsive homopolymers with a fastand reversiblemorphology transformation has attracted considerable focus but remainsa challenge. Herein, two perfectly regioregular polyolefin-like homopolymerscontaining azobenzene (azo) pendants on exactly every 11th or 21stcarbon atom, along with two regiorandom analogues have been synthesizedvia acyclic diene metathesis polymerization. The precision azo-homopolymersexhibited relatively shackling photoisomerization transition whilethe photoisomerization of random azo-copolymers transformed and recoveredcompletely, which led to strikingly different self-assembly behaviors.Notably, two azo-homopolymers initially self-assembled to uniformlydispersed nanospheres, and various morphological changes from one-dimensionalto two-dimensional directions were achieved by manipulating UV-lightirradiation time based on the synergy of regioregular polyolefin-likebackbone and noncovalent aromatic–aromatic interaction of azopendants, with the initial morphology recovered again under vis-lightirradiation. Remarkably, two regiorandom azo-copolymers assembliespresented the coexistence of nanospheres and nanowires, the subsequentlight-triggered shape transformation in three-dimensional directions,and the eventual restoration in one-dimensional direction. Overall,this work significantly enriched the family of polymeric assemblieswith reversible shape transformation, and the photoresponsive behaviorswere extremely sensitive, which provided further guidance for thedesign of stimuli-responsive self-assembly systems.

Upcycling polymer waste, especially polyamide 6 (PA6),remainschallenging because it is difficult to simultaneously exploit itsintrinsic structural advantages and meet the performance requirementsof high-value applications. Herein, we propose a structure-guidedupcycling strategy for the fabrication of high-performance adhesivesthrough the partial depolymerization of PA6 via glycolysis followedby directed molecular reconstruction. By incorporating rigid aromaticmoieties and flexible polyether soft segments into the reconstructedpolymer network, a compatible and controllable polymerization systemfor PA6 glycolysates was established. This structural design not onlypreserved high cohesive strength within the adhesive matrix but alsoenhanced interfacial interactions with diverse substrates, therebyenabling excellent bonding performance. The resulting adhesives exhibitedoutstanding adhesion strength toward various materials. In particular,the lap-shear strength toward different metals exceeded 15 MPa, withthe highest value of 22.9 MPa achieved on iron substrates. In addition,the adhesive displayed desirable practical features, including transparency,solubility, reusability, and stability under various aqueous conditions.Overall, the adhesive performance and multifunctionality of the obtainedadhesives compare favorably with those of previously reported polyamide-basedadhesives. This work provides a practical and efficient route forthe high-value upcycling of polyamide waste.

Hydroxyl-terminated poly(butadiene) (HTPB) is the preeminentprepolymeremployed in binders for solid-rocket motors. While well-known andcapable of providing favorable mechanical properties, the synthesisof HTPB is uncontrolled, leading to a lack of uniformity between samples,and, as a pure hydrocarbon, it provides little additional energy tothe grain. In this work, we demonstrate the use of ring-opening metathesispolymerization to prepare HTPB that is perfectly telechelic and easilydoped with strained cyclobutyl groups via the comonomer δ-pinene,adding additional energy to this otherwise inert polymer through theuse of an abundant, domestic source. We report structural, thermochemical,and rheological properties as well, demonstrating the utility of thispolymer in applications relevant to solid-rocket motors. Computationalinvestigations into the ring-strains of the monomers are reported,providing insight into their relative reactivity in the copolymerizationreaction.

Waterborne fluoroethylene vinyl ether (FEVE) fluorocarboncoatingsrepresent an attractive platform for high-performance protective applications,offering significant advantages in reducing organic solvent usageand improving environmental and human health safety. However, theirpractical development is critically hindered by inherent incompatibilities:the low surface energy of fluorinated latex particles and the poorwater compatibility of conventional isocyanate curing agents oftenlead to defective film formation, including mismatched cross-linking,phase separation, porosity, and cracking. To address these challenges,we designed and synthesized a hydrogen-bond-enriched latent curingagent based on adipic dihydrazide (ADH)-modified methyl ethyl ketoxime(MEKO)-blocked hexamethylene diisocyanate (HDI). Thermal analysisrevealed that low ADH contents preserve the primary melting behaviorof HDI-MEKO at approximately 76–77 °C, while maintainingthe main thermal activation within 150–200 °C, supportinga ″film formation prior to deblocking cross-linking″curing mechanism. Comprehensive coating evaluations demonstrate thatlow-to-moderate ADH incorporation achieves an optimal balance amongfilm morphology, adhesion, hardness, hydrophobicity, and chemicalresistance. Notably, HDI-MEKO-05-F and HDI-MEKO-15-F films exhibitrelatively smooth morphologies, grade 0 adhesion, and a 4H pencilhardness. This study provides a feasible and effective strategy forcoordinating latex film formation, thermal deblocking, and chemicalcross-linking, thereby facilitating the development of advanced, high-performancewaterborne FEVE coatings.

As high-frequency communication technologiesshift carrier frequenciesinto the millimeter-wave regime, legacy protective substrates showincreasingly poor electromagnetic transparency, creating a fundamentalmismatch between their wave-transmitting capability and the stringentlow-loss requirements of next-generation communication architectures.Polyimide aerogel substrates, characterized by ultralow dielectricconstant and loss, sufficient mechanical strength, and moisture resistance,have garnered significant attention. 2,2′-Bis(trifluoromethyl)-4,4′-diaminobiphenyl(TFMB) as a fluorinated monomer and more economical modified carbonfibers as crosslinkers were introduced to prepare a polyimide aerogel.The polyimide aerogel exhibits an exceptionally high porosity of >93%,with an average pore size ranging from 15.2 to 27.0 nm. Their dielectricconstant ranges from 1.05 to 1.11, with dielectric loss between 0.112%and 1.025% (8.2–12.5 GHz). With their unique combination ofultralow density, excellent mechanical properties, high thermal stability,low thermal conductivity, and moisture resistance, our polyimide aerogelsare highly promising for high-frequency communication applications.

The development of fluorine-free proton exchange membranes(PEMs)is crucial for reducing the environmental concerns associated withperfluorinated membrane materials. Herein, we report a series of sulfonatedpolytriazoles (SPTs; TABPSH-XX) via simple “click” copolymerization,wherein phosphine oxide (P═O) units are strategically integratedinto both hydrophilic and hydrophobic sections of the copolymer framework.The development of high-molar-mass copolymers is confirmed by viscosityand SEC analyses. Their chemical architectures are confirmed by theNMR (¹H, ¹³C, and ³¹P), XPS, andEDX analyses. The TABPSH-XX copolymers exhibit ion exchange capacitiesranging from 1.84 to 2.27 mequiv/g. Morphological studies reveal well-developed,interconnected, hydrophilic–hydrophobic phase-separated microstructureswith defined interfaces, facilitating efficient proton transport.The incorporation of high proportions of P═O functionalitiespromotes strong ionic and acid–base interactions, resultingin membranes with excellent thermal, mechanical, and dimensional stability.Among the series, the TABPSH-90 membrane exhibits the highest protonconductivity (121 mS/cm) at 90 °C under fully hydrated conditionsand demonstrates enhanced oxidative stability (≥6.5 h). Thesefindings demonstrate an effective molecular design strategy for developinghigh-performance fluorine-free sulfonated PEMs and highlight the potentialof P═O-enriched SPTs for next-generation membrane-based electrochemicalapplications.

Mixed-matrix membranes were preparedfor methanol (MeOH)/dimethylcarbonate (DMC) pervaporation by incorporating UiO-66-(COOH)₂, UiO-66-NH₂, or polyethylenimine-functionalized UiO-66-NH₂ (UiO-66-N-PEI) at the same nominal loading of 2.5 wt % intosulfosuccinic acid-crosslinked poly(vinyl alcohol) (PVA). The distinctivecontribution of this study is a controlled, side-by-side comparisonof carboxyl-, primary-amine-, and PEI-modified UiO-66 fillers withinthe same polymer matrix, crosslinking formulation, fabrication procedure,and operating conditions. Characterization showed that functionalizationaltered not only the filler surface chemistry but also particle sizeand accessible porosity. UiO-66-N-PEI exhibited the lowest BET surfacearea and pore volume and produced a thin, continuous selective layer.At 40 °C with a feed containing 10 wt % MeOH, its incorporationdecreased membrane swelling from 18.25 ± 2.04% for pristine PVAto 6.69 ± 0.90%, while increasing the MeOH/DMC sorption selectivityfrom 421.04 to 945.18. The UiO-66-N-PEI/PVA membrane consequentlyexhibited the highest separation factor of 601 while maintaining apermeation flux of 642 g·m^–2·h^–1. Stable performance was maintained during 7 days of operation underthese conditions. When the feed MeOH concentration increased to 70wt %, the flux increased to 1689 g·m^–2·h^–1, whereas the separation factor decreased to 2.67,revealing a transition toward swelling-dominated transport near theazeotropic composition. These findings show that the observed performanceresults from the coupled effects of PEI-associated functionality,reduced pore accessibility, altered polymer packing, and swellingresistance rather than surface wettability alone. The optimized membraneis therefore more effective for removing residual MeOH from DMC-richstreams, while additional swelling control is required for efficientnear-azeotropic separation.