ACS Applied Polymer Materials最新文献

Developing sensitive temperature sensors for nano- and microscale applications has become critical in many technologies and scientific fields. Such sensors enable the accurate measurement and control of temperature in extremely small domains, providing unparalleled insights into thermal behaviors and properties. In this study, we tune the photophysical properties of a short poly(phenylene ethynylene)-type (PPE-CO₂) conjugated polyelectrolyte (CPE) using poly(diallyldimethylammonium chloride) (PDDA), a positively charged polyelectrolyte, to develop a self-referenced fluorescence-based temperature sensor. In the presence of PDDA, PPE-CO₂ is initially quenched, but a small fraction of the disaggregated CPEs are believed to be stabilized. This in turn provides a thermally stable signal at 465 nm, which serves as an internal reference. The fluorescence intensity at 525 nm of the aggregated CPE maintained its thermal dependency which, when referenced with the 465 nm peak, created a sensitive and stable temperature sensor. The thermal response was further enhanced at low ionic strength. Specifically, without NaCl, individual polymers are less solubilized, minimizing fluctuations at the 465 nm peak and leading to higher thermal sensitivity and a wider linear range. The thermal response for PDDA/PPE-CO₂-108 was tested between 20.0 and 90.0 °C, with optimized sensitivities of 0.0028 and 0.0038 °C^1– with and without NaCl, respectively. Relative sensitivity (S_r) was 4.9% °C^1– at 20 °C for PDDA/PPE-CO₂-108 without NaCl.

Cross-linked conjugated polymers show many unique performance advantages in ionic transport, stretchability, and cycle stability. However, the relationship between cross-link density and performance is always ignored in designing cross-linked conjugated polymers. Here, a series of poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives with different cross-link densities were prepared by two steps: (1) free radical polymerization of flexible side chain (methacrylate); (2) electrochemical copolymerization of conjugated units (thiophene derivatives). These cross-linked conjugated copolymers except for poly(2,1) with high cross-link density exhibit a similar optical absorption region with a definite peak, indicating that low cross-link density has little influence on the absorption region. Electrochromic results indicate that poly(1,10) with low cross-link density possesses a higher optical contrast (70%) and faster response time (0.5 s) than linear poly(ProDOT-Me) and other cross-linked conjugated copolymers with relatively higher cross-link density. When cross-link density is beyond a critical value, it could be also found that the electrochromic properties of conjugated polymers decrease gradually as the cross-link density increases. And the flexible electrochromic device (10 cm × 6 cm) based on poly(1,10) was constructed, whose color could reversibly turn between purple and transmissive blue. These results demonstrate that controlling cross-link density is essential in designing cross-linked conjugated polymers as electrochromic materials.

Rigid polyurethane foam (RPUF) shows great application potential in the fields of architecture, household, and transportation due to its lightweight, durability, and excellent heat insulation. However, it remains challenging to construct flame-retardant and impact-resistant RPUF composites with good thermal insulation through a facile approach. Herein, multifunctional hierarchical RPUF composites were prepared by simple one-pot foaming and brush-coating methods. Due to the hierarchical structure and multifunctional polyborosiloxane/phytic acid/polyethylenimine (PBS/PAP) coating, the as-created foams displayed excellent fire safety and impact resistance. For instance, the peak of heat release rate and total heat release of the RPUF composite with the PBS/PAP coating decreased by 70.1 and 57.0%, respectively, relative to those of pure RPUF. Furthermore, the composite showed good heat insulation and improved thermal stability performance. This work offers a paradigm for the design of multifunctional RPUF composites with outstanding fire resistance, impact resistance, and heat insulation properties, which represent prospective potential in safety protective materials.

The dual-percolation polybutene-1 (PB)/poly(ethylene-co-octene) (POE)/carbon nanotube (CNT) composite foams with lightweight, high conductivity, and high-efficiency EMI shielding performance were successfully prepared via melt blending followed by supercritical carbon dioxide (sc-CO₂) foaming. The CNTs’ selective location in the PB phase of PB/POE/CNT composites was verified based on the kinetic/thermodynamic predictions and scanning electron microscopy observations. The dual percolation structure and porous microstructure of composites affecting the electrical conductivity and EMI shielding property were carefully evaluated. Owning to the bimodal porous structure of dual-percolation composite foams, in which large pores contributed to increasing porosity and small pores dedicated to maintaining the connectivity in conductive networks, the high void fraction and high conductivity were simultaneously achieved. The electromagnetic interference (EMI) shielding performance showed that the foamed PB/POE/CNT composites with 1.4 vol % CNTs loading displayed a 71% decrease in density, 43.2% increase in absorptivity, 41.1% increase in EMI shielding effectiveness (SE), and 76.4% increase in specific EMI SE, in comparation with the solid PB/POE/CNTs loaded with 1.6 vol % CNTs. Moreover, the foamed PB/POE/CNT composites with a 3.3 vol % CNT loading achieved a high EMI SE of 22.4 dB, satisfying the requirements of commercial EMI shielding materials (≥20 dB).

In the field of advanced materials science, the application of aluminum ions as dynamic metal salt cross-linkers in self-healing polymers has been less prevalent compared to transition or rare earth metal ions, attributable to the relatively modest self-healing and mechanical properties of aluminum ions. Our study introduces an alternative strategy by combining aluminum ions with acetylacetonates (acac^–) as counteranions and integrating a pyridine-capped polyurethane-urea polymer backbone (PTD) and phosphorus-rich small molecules (3N2AP) to develop a composition, Al_ac-3N2AP-PTD. This formulation exhibits phosphorus-based flame retardancy, improved self-healing capabilities, and enhanced mechanical properties. It demonstrates superior performance compared to existing aluminum-based systems and is competitive with traditional transition metal ion-based systems. To elucidate the underlying mechanisms of these enhancements, molecular dynamics (MD) simulations were conducted to examine the coordination dynamics and the effects of counteranions within the polymer network. The simulation results indicated longer coordination bond lengths in the system incorporating acac^–, supporting its efficacy and clarifying the mechanisms contributing to the increased self-healing capabilities and mechanical robustness. In our development of a stretchable, self-healing, and conductive composite, we fabricated PPy-Al_ac-0.25-3N2AP-PTD via an electrochemical deposition process. This material acts as an electronic skin (e-skin) strain sensor, exhibiting strain sensitivity while preserving its inherent mechanical and self-healing properties, thus differentiating it from traditional doping methods. The use of acac^– as dynamic counteranions in metal-coordinated polymers represents an advancement in material performance, offering substantial potential for the development of electronic materials.

Flexible sensors have outperformed traditional rigid sensors in healthcare and sports monitoring due to their flexibility and comfortableness. However, wearable sensors are susceptible to signal interference and external corrosion, leading to early failure of sensing performance. Inspired by the self-cleaning property of the surface microstructure of lotus leaves, we have designed a superhydrophobic flexible sensor of L-CNT@PDMS by a template method and a laser direct writing technique. Single-walled carbon nanotubes (CNTs) were incorporated into poly(dimethylsiloxane) (PDMS) to prepare a CNT@PDMS elastomer. Then, microcolumn arrays were generated by picosecond laser ablation. The effects of laser power density and micropillar structural parameters on wettability and sensing properties were investigated. The prepared L-CNT@PDMS sensor showed excellent superhydrophobicity (CA > 151°, SA < 3°), mechanical strength (breaking elongation of 110% and breaking stress >18 MPa), anticorrosion properties, and good sensitivity (gauge factor of 267). Meanwhile, the L-CNT@PDMS sensor possessed superior photothermal/electrothermal properties, showing delayed icing and deicing effects. These laser-textured superhydrophobic flexible sensors of L-CNT@PDMS with comprehensive performance have great potential applications in healthcare, motion monitoring, and underwater equipment.

Antismudge coating materials are generally synthesized by using petroleum-based polyols and fluorinated compounds, which are harmful to the environment and human health. Thus, researchers are more inclined to develop polyurethane (PU) coating from biobased polyols and fluorine-free materials. Here, silicone-containing diol was used with soybean oil polyol (SOP) to produce a PU coating. The chemical inertness to acid, base, and salt, along with the nonstick properties of silicone, would help achieve the desired properties of the antismudge PU coating. Metal (stainless steel) and wood coupons (oak wood) were coated with this synthesized coating material and tested to study the chemical resistance along with an ink test. In addition, the coated metal coupons were subjected to water and solvent drops more than 50 times without any discernible influence on the metal. Contracted ink was used to write 1000 times on the coating, and ink was easily erased by a paper napkin. The coating material was also subjected to a burning test, and the ignition time increased in direct correlation with the proportion of the Si-containing diol. More than twice as long as the control sample, 11 s were required for Si-40 wt % to start burning. The weight loss achieved with Si-40 wt % PU coating material is only 1%. Furthermore, after being immersed in water for 24 h, these PU coating materials failed to demonstrate any discernible impact. With a water contact angle of 95°, this PU coating material is hydrophobic. The coatings were exhibited to test their ability to absorb solvents as well as heat analysis. All available results suggest that environmentally friendly materials are promising candidates for future surface protective coatings.

A hygroscopic layer plays an important role in improving the output abilities of energy generation from ubiquitous moisture, whose mechanism is unclear. Herein, three kinds of hydrogels with different pore structures/functional groups are designed as hygroscopic layers, and a universal strategy was proposed to assemble them into hydrogel-based moisture-electric generators (HMEGs). The hydrogels’ pore structure affects the moisture absorption rate, while the functional groups regulate the diffusion path of water. HMEG’s power generation is a synergistic effect of ionic diffusion and streaming potential, which is closely related to the water diffusion within the material and is not directly related to the amount of moisture absorption. HMEG, which absorbs moisture quickly, stores water efficiently, and releases moisture slowly, has an excellent performance and stable voltage output. Based on this mechanism, HMEG employed the calcium chloride-poly(vinyl alcohol)-poly(N-isopropylacrylamide) (CPVPN), semi-interpenetrating network (semi-IPN) hydrogel as the hygroscopic layer showed an open-circuit voltage as high as 0.34 V and a power density of 33.23 μA cm^–3. This study opens a perspective on hydrogel HMEG and provides insights into high-performance HMEG design.

We report here a high-value-added strategy for the chemical recycling of poly(butylene terephthalate) (PBT) into poly(ethylene brassylate-co-butylene terephthalate) (PEBBT) copolyesters. By cyclodepolymerization, postconsumer PBT can be first depolymerized to attain cyclic oligo(butylene terephthalate)s (COBTs), which are further copolymerized with ethylene brassylate (EB) and 1,10-decanediol for the preparation of PEBBT copolyesters using a cascade polycondensation coupling ring-opening polymerization (PROP) method. The chemical structures of PEBBT copolyesters are carefully characterized through quantitative ¹H and 2D ¹H–¹H gCOSY NMR spectroscopies. By changing the initial feeding ratio of COBTs and EB, the contents of aromatic and aliphatic polyester segments in PEBBT can be flexibly tuned, which can be further used to modulate the crystallinity, mechanical and biodegradable properties. These PEBBT copolyesters exhibited remarkable mechanical performance with high strength, elongation at break and toughness. Moreover, in the presence of lipase, complete biodegradation can be achieved for copolyesters with high aliphatic polyester segment contents.