ABSTRACT
It is understood that the ballistic resistance of aromatic polyamide fibers is related to the fiber's ultimate tensile strength, strain‐to‐failure, and Young's modulus. Ideal ...high‐performance ballistic materials maximize these properties while minimizing material density. Equally important is long‐term mechanical and chemical stability: the fibers should not exhibit performance loss over their lifetime. However, less is known quantitatively about their modes of degradation, and experimental methods to quantify the aging and degradation in these fibers are critical. Multiple variations of next generation high‐performance fibers have been investigated under chemical and mechanical accelerated aging conditions. Performance losses have been empirically correlated to chemical degradation of the polymer chain and nanostructural changes in the fiber morphology through X‐ray photoelectron spectroscopy (XPS). Here, we introduce positron annihilation lifetime spectroscopy measurements as a sensitive method to quantify the early onset of damage in the flexed fibers as quantified through changes in the nanoscale void structure in the material. Published 2017.† J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1711–1717
Methods of rapidly assessing aging and degradation of high performance polymer fibers are critical for designing next‐generation materials. Three polymer fiber types were investigated under accelerated aging conditions. Single fiber tensile behavior of the aged samples varied based on the chemical and nanostructural composition of the fibers. Fiber nanostructure was characterized with positron annihilation lifetime spectroscopy to measure the onset of changes in free volume and void formation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Mimicking the hierarchical brick‐and‐mortar architecture of natural nacre provides great opportunities for the design and synthesis of multifunctional artificial materials. The crucial challenge to ...push nacre‐mimetic functional materials toward practical applications is to achieve ample ductility, toughness, and folding endurance with simultaneously maintaining high‐level functional properties. In this study, the microstructure of nacre‐mimetics is reformed through predesigning a 3D nanofiber network to replace conventional polymer matrices. A unique sol–gel–film transformation approach is developed to fabricate a graphene‐based artificial nacre containing a preforming 3D, interconnective, inhomogeneous poly(p‐phenylene benzobisoxazole) nanofiber network. The fabulous coupling of the extensive sliding of graphene nanoplatelets and intensive stretching of the 3D nanofiber network over a large scale enables the artificial nacre to display natural nacre‐like deformation behavior, achieving ultralarge strain‐to‐failure (close to 35%), unprecedented toughness (close to 50 MJ m−3), and fold endurance (no decrease in tensile properties after folding for 10 000 times or folding at increasing stress). The new levels of ductility, toughness, and folding endurance are integrated with outstanding thermal properties, including thermal conductivity (≈130 W m−1 K−1), thermal stability (520 °C) and nonflammability, rendering the lightweight nacre‐mimetics promising in flexible electronic devices, particularly for aerospace electronics.
With a predesigned 3D interconnective nanofiber network as the matrix, graphene‐based nacre‐mimetics achieves unprecedented ductility (≈35%), toughness (≈50 MJ m−3), and folding endurance (10 000 folding cycles, folding at 20 MPa and arbitrary kneading) with simultaneous integration of high‐level functional properties (thermal conductivity, thermal stability, and nonflammability). This microstructure concept opens the door for fabricating tough, functional bioinspired materials toward practical applications.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The construction, performance characteristics and application of a novel copper (II) membrane sensor based on a new Dimethyl 4, 4′-(o-phenylene)bis(3-thioallophanate) are reported in this paper. The ...designed sensor exhibited a wide linear response with a slope of 30.3mV per decade over the concentration range of 9.8×10−6–1.0×10−1M. The potentiometric response is independent on the pH of the solution in the range of 3.1–7.6. The electrode shows a response time of 20s. The proposed electrode can be used for at least two months without any considerable divergence in potentials. It exhibits very good selectivity relative to a wide variety of alkali, alkaline earth, transition and heavy metal ions. The developed sensor was used for the quantitative determination of Cu (II) ions both in synthetic and real samples. The electrode assembly was also used as an indicator electrode in the potentiometric titration of Cu2+ with EDTA.
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► A new membrane material has been used for copper ISE. ► Sensor shows Nernstian slope, wide linear response and working pH range. ► Sensor shows short response time, long lifetime. ► Highly selective over alkali, alkaline earth, and transition metal ions ► Can be used for quantitative determination of Cu(II) in synthetic, real samples
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The backbone stability of benzyl-trimethyl ammonium (BTMA) functionalized polyaromatics was investigated in two structurally differing polymer architectures; quaternized poly(arylene ether) (PAE) and ...poly(phenylene) (PP). FTIR analysis indicated the cleavage of aryl-ether linkages in quaternized PAEs under high pH environments, while no backbone degradation in quaternized PP was observed. The backbone degradation of PAEs not only significantly reduced the mechanical properties of the membranes, but also negatively impacted hydroxide conductivity. Membrane electrode assemblies (MEAs) using both PAE and PP membranes showed good initial alkaline membrane fuel cell performance. However, the PAE MEA displayed larger performance losses and failure after only 55h, due to a mechanical breach. No catastrophic failure of the PP MEA occurred after 300h, which further confirmed the stability of the polymer backbone.
► Systematically investigated the polymer backbone degradation for poly(arylene ether) anion exchange membranes. ► Proposed the backbone degradation mechanism from FTIR and GPC results. ► Compared the degradation rate of polymer backbone and cation functional group. ► Addressed the impact of polymer backbone degradation on polymer properties and fuel cell performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The synthesis of structurally well‐defined, monodisperse carbon nanotube (CNT) sidewall segments poses a challenge in materials science. The synthesis of polyphenylene cylinders that comprise typical ...benzene connectivity to resemble precursors of 9,9 and 15,15 CNTs is now reported, and the products were characterized by X‐ray crystallography. To investigate the oxidative cyclodehydrogenation of ring‐strained molecules as a final step towards a bottom‐up synthesis of CNT sidewall segments, phenylene‐extended cyclic p‐hexaphenylbenzene trimers (3CHPB) were prepared, and NMR studies revealed a strain‐induced 1,2‐phenyl shift. It was further shown that an increase in ring size leads to selectively dehydrogenated macrocycles. Larger homologues are envisioned to give smooth condensation reactions toward graphenic sidewalls and should be used in the future as seeds for CNT formation.
Tube design: Polyphenylene cylinders that resemble precursors of carbon nanotubes (CNTs) have been synthesized and characterized by X‐ray crystallography. The oxidative cyclodehydrogenation was investigated for ring‐strained molecules as a final step towards a bottom‐up synthesis of CNT segments, and revealed strain relief through a 1,2‐phenyl shift.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We demonstrate a silver-sulfur (Ag-S) coordination reaction induced in-situ interfacial enhancement approach for fabricating robust, corrosion resistant, thermal conductive and fire resistant PPS/Ag ...shielding composites with ultra-efficient 3D Ag conductive network.
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•A multifunctional and ultra-efficient EMI shielding PPS/Ag composite is fabricated.•Ag-S coordination reaction induces in-situ interfacial enhancement in processing.•The composite with perfect 3D Ag network exhibits an EMI SE of 87.8 dB in X-band.•The composites exhibit good strength, thermal conductivity and corrosion resistant.•The multifunctional composites show great shielding stability in harsh environment.
Lightweight, multifunctional and highly efficient electromagnetic interference (EMI) shielding polymer composites with reliable EMI protection, efficient heat dissipation, excellent fire safety, and corrosion resistance are highly desired for next-generation electronic devices and high-power electronic communication technologies. However, developing robust and multifunctional conductive polymer shielding composites to meet stringent requirements when in harsh application environments remains a great challenge. Herein, a multi-functional and highly efficient EMI shielding poly(phenylene sulfide) (PPS) composite with a perfect 3D silver (Ag) conductive network and enhanced interfacial connection is fabricated through a unique silver-sulfur coordination reaction-induced in situ interfacial enhancement approach. The prevalent silver-sulfur coordination reaction between the PPS matrix and 3D Ag network provides the Ag/PPS composite with strong interfacial interaction and a reliable conductive network, leading to superior electrical conductivity, ultra-efficient EMI shielding effectiveness (87.8 dB), excellent thermal conductivity (1.15 Wm-1K−1), remarkable corrosion resistance and satisfactory mechanical properties (~60 MPa) at very low Ag contents. Moreover, the multi-functional shielding composite also exhibits marvellous anti-friction and wear-resistant performance along with excellent fire resistance and antibacterial properties. Therefore, the silver-sulfur coordination reaction-induced in situ interfacial enhancement during facile thermal compression moulding creates a multi-functional and robust EMI shielding composite, which is promising for conferring ideal EMI protection to next-generation electronics in complex application environments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Go to three dimensions: As a step toward a bottom‐up synthesis of size‐defined carbon nanotubes (CNTs), 3cyclo‐4′,4′′′′‐hexaphenylbenzenes (3CHPBs) were synthesized and investigated. Theoretical and ...experimental results revealed that 3CHPBs possess highly twisted 9cyclo‐p‐phenylene cores. 3cyclo‐2,11‐(Hexa‐peri‐hexabenzocoronene) (3CHBC) was also examined for CNT synthesis (see figure).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Enzymes immobilized in matrices like conducting polymers (CPs) can form a supramolecular structure with enhanced biosensing performance, which depend on the structural polymer properties. This ...present paper employed CPs from the classes of thiophenes, fluorenes, phenylenes, and phenylene-vinylenes to immobilize urease as thin films and to investigate the relationship between the film structure and the enzyme activity. The films were assembled by the spin coating technique and characterized by UV–vis, fluorescence, and infrared spectroscopies. The enzymatic activity was estimated with UV–vis spectroscopy. Films containing different CPs presented specific enzyme activities dependent on polymers' size and polydispersity, but these activities were independent of their specific conductivity. Poly (9,9-dioctylfluorene-co-phenylene) (PFPh) presented the lower KM constant (1.52 mM.s−1) and was the polymer with lower molecular weight and polydispersity. The results suggested that small and homogeneous size chains increase the enzyme activity, which can be beneficial, generally speaking, for the construction of based-enzyme biosensors with enhanced efficiency.
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•The relationship between the matrix structure and urea biosensor was studied.•CPs of different classes were used in the immobilization of the urease enzyme.•The polymers’ size and polydispersity directly influence the enzymatic activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The variation of the drift mobility of positive and negative charge carriers in films of anthracene‐containing poly(p‐phenylene‐ethynylene)‐alt‐poly(p‐phenylene‐vinylene)s (AnE‐PVs), differently ...substituted, is investigated as a function of the applied electric field. Branched 2‐ethylhexyl and linear alkoxy side chains of different lengths are considered, as well as well‐defined and random distributions of lateral substituents. The same conditions are used both for the deposition of the polymer films and for their characterization, which allows for the establishment of a clear relationship between the chemical structure and the charge carrier mobility.
Charge transport is investigated in a series of anthracene‐containing poly(p‐phenylene‐ethynylene)‐alt‐poly(p‐phenylene‐vinylene)s with the same conjugated backbone. The nature of the solubilizing alkoxy lateral chains has a great impact on the charge‐carrier mobility, with a variation observed of 2–3 orders of magnitude.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
ortho‐Phenylenes are one of the simplest classes of aromatic foldamers, adopting helical geometries because of aromatic stacking interactions. The folding and misfolding of ortho‐phenylenes are slow ...on the NMR timescale at or below room temperature, allowing detection of folding states using 1H NMR spectroscopy. Herein, an ortho‐phenylene hexamer is coupled with a RAFT chain transfer agent (CTA) on each repeat unit. A variety of acrylic monomers are polymerized onto the CTA‐functionalized ortho‐phenylene using PET‐RAFT to yield functionalized star polymers with ortho‐phenylene cores. The steric bulk of the acrylate monomer units as well as the chain length of each arm of the star polymer is varied. 1H NMR spectroscopy shows that the folding of the ortho‐phenylenes do not vary, providing a robust helical core for star polymer systems.
PET‐RAFT polymerization is used to prepare six‐armed star polymers with ortho‐phenylene foldamer cores and polymer arms. Polymerization is efficient for a range of functional monomers with good control over molecular weights. 1H NMR spectroscopy shows that the ortho‐phenylenes remain helically folded despite changes in arm steric bulk, hydrophobicity, and length.
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