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Polyimide (PI) has good mechanical properties and thermal stability, while high coefficient (COF) and wear rate limit its wide application. In order to endow PI with better friction and wear resistance, Mo2Ti2C3 MXene was used as solid lubricant to prepare Mo2Ti2C3/PI nanocomposites with different content of Mo2Ti2C3. The effect of the amount of Mo2Ti2C3 on the tribological behavior of PI was explored and the tribological mechanism was also analyzed Tribological tests showed that at 1.2 wt% of Mo2Ti2C3 addition, the composite material demonstrated superior friction and wear resistance, exhibiting a 19.9% decrease in the COF and a 79.7% decrease in the wear rate compared to single PI due to the good self‐lubricating properties of Mo2Ti2C3 MXene. Moreover, Mo2Ti2C3 can also effectively assist PI to form sleek transfer films without interruption or gaps on the steel balls, resulting in a reduced friction COF and wear rate of the material. This work demonstrates that Mo2Ti2C3 MXene is an aussichtsreich additive for polymers to improve the tribological properties and broadens the applications of Mo2Ti2C3/PI composites in friction material area. Highlights: Mo2Ti2C3 significantly improves the tribological performance of polyimide.The thermal properties of Mo2Ti2C3/polyimide are enhanced by the introduction of Mo2Ti2C3.The minimum coefficient of Mo2Ti2C3/PI composites was only 0.246 at the 1.2 wt% content of Mo2Ti2C3.The wear rate of Mo2Ti2C3/PI composites was decreased by 79.7% at the 1.2 wt% addition of Mo2Ti2C3.Mo2Ti2C3 promotes the establishment of tribo‐film to protect the Mo2Ti2C3/PI composites from friction. [ABSTRACT FROM AUTHOR]

Polyimide (PI) is a special engineering plastic, widely involved in mechanical components, instruments, and petrochemicals. However, single PI material is inevitably subject to wear and tear in practice, which leads to weakened material properties. In this work, Ti3C2Tx@SiO2 was prepared to enhance the wear resistance and lubrication properties of PI by intercalating SiO2 into the interlayer of Ti3C2Tx sheets. Ti3C2Tx@SiO2/PI composites were fabricated in two steps to test the tribological performances. SiO2 particles change the form of interfacial friction from sliding to rolling, thus relieving direct friction between material and steel ball. So, the composites have a minimum COF (COF = 0.33) when the content of Ti3C2Tx@SiO2 is 0.80 wt%. Moreover, the average value of wear rate was 0.24 × 10−5 mm3/(N·m) when Ti3C2Tx@SiO2 content was 1.60 wt%, which was 91.0% lower compared to the PI matrix. During the friction process, the abrasive chips of the material migrate to the surface of the steel ball to form a transfer film, which protects the material and thus reduces the wear rate. Therefore, the hybrids Ti3C2Tx@SiO2 are effective and important wear‐resistant agents and solid lubricants to improve the wear resistance and lubricity of PI or other polymer materials. Highlights: SiO2 insert Ti3C2Tx is a key factor in changing sliding friction into rolling friction, effectively reducing the COF.The average wear rate was 91.0% lower than that of the polyimide matrix when Ti3C2Tx@SiO2 content was 1.60 wt%.The minimum COF of Ti3C2Tx@SiO2/PI composites reached 0.33 when the content of Ti3C2Tx@SiO2 was 0.80 wt%.The transfer film effectively reduces further wear of the material during friction. [ABSTRACT FROM AUTHOR]

Thin‐thickness and lightweight electromagnetic wave (EMW) absorption materials are critically needed for stealth technology in the military stealth field. The special structure of a material is important for improving its good EMW absorption. Herein, a series of porous metal–organic framework‐derived LaCo/C‐decorated Ti3C2Tx (LaCo/C/Ti3C2Tx) composites are prepared by carbonization at high temperatures. Impressively, the minimum reflection loss of LaCo/C/Ti3C2Tx–2 is −47.72 dB at 10.26 GHz (thickness 2.3 mm), and the optimal effective absorption bandwidth is 5.45 GHz (thickness 1.9 mm). The excellent EMW absorption properties are due to multiple electromagnetic loss mechanisms, such as polarization loss, magnetic loss, and multiple reflections and scattering. This work provides a new route for the application of Ti3C2Tx‐based derivatives. [ABSTRACT FROM AUTHOR]

A series of polyimide (PI)/V2CTx MXene composites was synthesized via polyamide acids (PAA) and two‐dimensional (2D) V2CTx MXene obtained by etching precursor V2AlC. PI/V2CTx MXene composites with different mass ratios were obtained by blending and heating with PAA. The results showed that V2CTx MXene has excellent dispersion in PI. In particular, V2CTx MXene exhibited excellent friction reduction and anti‐wear properties as a solid lubricant additive, and the wear rate (WR) was reduced by 43.2% by incorporating only 0.8 wt% of V2CTx MXene in the pristine PI and 71.9% by incorporating 1.2 wt%. Scanning electron microscopy (SEM) and x‐ray photoelectron spectroscopy (XPS) analyses showed that the continuous transfer film consisting of a high proportion of tribo‐chemical products formed on the contact surface is significant to improve the lubrication performances of the PI composites. This work broadens the application of MXene in the field of tribology and contributes to energy conservation and sustainable development of human society. Highlights: The tribological properties could be tuned by changing the ratio of PI to V2CTx MXene.The WR of PI composites was reduced by 71.9% with incorporating 1.2 wt% of V2CTx MXene.The formation of transfer films on the contact surface is significant for improving anti‐wear of PI. [ABSTRACT FROM AUTHOR]

Solid lubricant materials could be used in various extreme conditions owing to the excellent anti‐friction and ‐wear with the low friction coefficient and wear rate. Polyurethane (PU)‐based solid lubricants as one of the widely utilized composite materials had been well‐known by researchers all over the world. PU‐based composite lubricants were commonly segmented into single‐phase lubricants and multi‐phase lubricants via inorganic or organic lubricant additives. What is more, the modified PU by solid lubricants would endow higher tribological performances than that of single‐phase PU‐based lubricants. Based on the multi‐component synergy, the multi‐phase lubricants could significantly improve the PU matrix's lubrication and wear resistance and enhance the comprehensive performance such as corrosion resistance. This paper mainly discussed and summarized the recent development in tribological performances of PU‐based composite lubricants, and explored their prospective research directions. [ABSTRACT FROM AUTHOR]

Herein, two types of tribocouple pairs based on polymer‐like carbon (PLC) films are designed through the in situ‐formed MXene coating. The in situ‐formed MXene coatings are synthesized via the in situ organic–inorganic chemical composite technique‐induced anionic polymers with different molecular weights (≈450 000 and ≈4 000 000, respectively). Next, the tribotesting condition is controlled in the ambient environment under different loads by bare and PLC‐coated bearing steel balls as counterbodies. During the whole sliding process, a lubricity state (friction coefficient is about 0.21 and wear rate is about 1.5 × 10−6 mm3 N−1 m−1) is realized on the self‐mated PLC system. Meanwhile, the contact surfaces are covered by graphitic 2D Ti3C2. Compared with the high‐molecular‐weight modifier system, most poly(acrylic acid)‐co‐MXenes grafted by the low‐molecular‐weight poly(acrylic acid) form far more sp2‐C phases. Moreover, active groups are potentially involved in forming a tribofilm, which enhances the overall lubricity of MXenes during sliding. This verifies the key to achieving low friction and ultralow wear based on the formation of the nanostructured sliding interface upon MXenes and provides an expanded application of solid lubricants. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: ZIF‐8 with excellent chemical and physical properties is a promising material for the field of electrochemical sensing. However, the poor electrical conductivity of ZIF‐8 severely limits its electrochemical performance. Here, we report a method that can significantly improve the conductivity of ZIF‐8 by intercalating Ti3C2Tx MXene as a conductive platform. Benefiting from higher conductivity and unique electrocatalytic activity, the obtained MXene/ZIF‐8 nanocomposite presented the worthy analytical performance for hydrazine sensing. The successful fabrication of MXene/ZIF‐8 holds great promise for the design of electrochemical sensors, and it is a promising material to promote the development of new electrode materials. [ABSTRACT FROM AUTHOR]

The triblock energetic copolymer poly(lactic acid)- block-(glycidylazide polymer)- block-polystyrene (PLA- b-GAP- b-PS) was synthesized successfully through atom-transfer radical polymerization (ATRP) of styrene and ring-opening polymerization of d,l-lactide. The energetic macroinitiator GAP-Br, which was made from reacting equimolar GAP with α-bromoisobutyryl bromide, firstly triggered the ATRP of styrene with its bromide group, and then the hydroxyl group on the GAP end of the resulting diblock copolymer participated in the polymerization of lactide in the presence of stannous octoate. The triblock copolymer PLA- b-GAP- b-PS had a narrow distribution of molecular weight. In the copolymer, the PS block was solvophilic in toluene and improved the stability of the structure, the PLA block was solvophobic in toluene and served as the sacrificial component for the preparation of porous materials, and GAP was the basic and energetic material. The three blocks of the copolymer were fundamentally thermodynamically immiscible, which led to the self-assembly of the block copolymer in solution. Further studies showed that the concentration and solubility of the copolymer and the polarity of the solvent affected the morphology and size of the micelles generated from the self-assembly of PLA- b-GAP- b-PS. The micelles generated in organic solvents at 10 mg mL−1 copolymer concentration were spherical but became irregular when water was used as a co-solvent. The spherical micelles self-assembled in toluene had three distinct layers, with the diameter of the micelles increasing from 60 to 250 nm as the concentration of the copolymer increased from 5 to 15 mg L−1. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article presents research on the effects of organophosphate content on flame retardancy, morphology and film properties of phosphorus-containing waterborne polyurethanes (WPU). In the study, a series of WPU with different reactive organosphate were prepared and characterized by Fourier transform infrared and proton nuclear magnetic resonance spectroscopy (H-NMR). The results showed that WPU films with phosphorus had lower onset and maximum degradation temperatures with higher char yields.

Nonconjugated bipolar transport polymers have been developed as host materials for electroluminescent devices by incorporating both electron‐transporting and hole‐transporting functionalities into copolymers. The random copolymer PCt‐nvk3‐7 containing mesogen‐jacketed segment of P‐Ct have been synthesized and characterized. The effect of mesogen‐jacketed segment content of these bipolar copolymers on device performance has been investigated. The results of polymer light‐emitting diodes (PLEDs) show that the jacketed content of copolymers has a significant effect on device performance: lowering charge transport and facilitating the hole‐electron recombination leads to much higher current efficiency. Applying these high triplet random copolymers as host, the maximum current efficiency of 0.70 cd/A and the maximum brightness of 1872.8 cd/m2 was achieved for PCt‐nvk3‐7 with an orange‐emitting complex dopant. The results suggest that the bipolar copolymers PCt‐nvks can be good host polymers for electrophosphorescent devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7861–7867, 2008 [ABSTRACT FROM AUTHOR]

Main observation and conclusion: ZIF‐8 with excellent chemical and physical properties is a promising material for the field of electrochemical sensing. However, the poor electrical conductivity of ZIF‐8 severely limits its electrochemical performance. Here, we report a method that can significantly improve the conductivity of ZIF‐8 by intercalating Ti3C2Tx MXene as a conductive platform. Benefiting from higher conductivity and unique electrocatalytic activity, the obtained MXene/ZIF‐8 nanocomposite presented the worthy analytical performance for hydrazine sensing. The successful fabrication of MXene/ZIF‐8 holds great promise for the design of electrochemical sensors, and it is a promising material to promote the development of new electrode materials. [ABSTRACT FROM AUTHOR]