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Polyhydroxyurethanes (PHUs), which are synthesized through the aminolysis of cyclic carbonates, avoid the use of toxic isocyanates compared with traditional polyurethanes (PUs) and have aroused great interest. The large number of hydroxyl groups in the network endows PHUs with unique features, such as recyclable properties and fluorescent properties. To establish the high performance and multifunctionality of PHUs, we designed a molecular structure to fabricate PHUs with mechanical robustness, shape memory properties, fluorescent properties, and recyclable properties. The yielded PHU crosslinked by the quaternary thiol and weak but dense hydrogen bonds (H‐bonds) shows unprecedented high mechanical properties with a tensile Young's modulus of 3.13 GPa, comparable to that of polyimide, a tensile strength of 59.2 MPa at room temperature and an excellent toughness of 27.9 MJ/m3 at 50°C, and good damping properties (tanδ ≥ 0.3, temperature range of 35.2°C). Interestingly, fluorescence caused by the aggregation of carbamate within PHUs allows it to be applied for damage self‐reporting to visualize tiny cracks or magnify fractures. Furthermore, both the thermosetting PHUs and recycled thermosetting PHUs presented excellent shape memory performance. This study provides certain inspiration for the design and development of highly rigid multifunctional polymers. [ABSTRACT FROM AUTHOR]

To make full use of the renewability of polylactide (PLA) and natural Eucommia ulmoides gum (EUG), novel fully sustainable thermal plastic vulcanizates (TPVs) with high toughness were developed via dynamic vulcanization technique based on modified EUG (referred to as EUG‐GMA). The latter greatly improved the toughness of PLA and the mechanism was discussed with respect to micro structure analysis. Aiming at providing theoretical guidance for PLA/EUG‐GMA TPVs in scratch related applications, the scratch behavior of TPVs with different EUG‐GMA content was studied in single‐pass and multiple‐pass scratching mode, after which the tribological mechanisms were discussed based on worn surface morphology and contact area analysis. It is revealed that the promoted interfacial adhesion due to in‐situ compatibilization and the co‐continuous phase structure of PLA/EUG‐GMA TPVs played crucial roles in enhancing the TPVs' toughness. In addition to tribo‐conditions, the above mentioned interfacial performance was also responsible for the variation of scratch behavior of different TPVs. It is expected that the present study would open up a new route of manufacturing sustainable composites combined with scratch resistance and toughness. [ABSTRACT FROM AUTHOR]

High‐order finite element method (FEM) has recently achieved significant success in solving acoustic problems and has proved to be accurate, robust, and capable of reducing the pollution effect. Inspired by the high‐order FEM, this study presents a novel high‐order collocation indirect BEM for solving three‐dimensional high‐frequency exterior acoustic problems. Due to the difficulty of evaluating hypersingular integrals on curved surface elements with complex density functions, the high‐order BEM scheme for acoustic problems has long been a challenging task, especially for relatively large‐scale problems. In the developed scheme, the Leis formulation is used to overcome the well‐known nonuniqueness problem in the indirect BEM, and an auxiliary integral equation method is presented and employed to regularize the hypersingular integrals in this formulation. The derived regularized boundary integral formulation is mathematically simple and amenable to the elements of arbitrary shape and arbitrary variable interpolation order, and leads to a simple, efficient, and robust algorithm for the calculation of all integrals. Several benchmark examples are investigated to verify the performance of the proposed method. Results demonstrate that the present method is very effective in stimulating the far‐field solution with large wavenumber. [ABSTRACT FROM AUTHOR]

Towards the goal of improving the tribological properties of epoxy‐based composites, epoxy resin was firstly modified with carboxyl terminated butadiene acrylonitrile (CTBN), and then further modified by core–shell structured of SiO2@MoS2 fillers. The friction and wear properties of studied composites were tested on a Plate‐on‐Ring configuration under different loads and speeds. To reveal the tribological contribution of MoS2 and SiO2 in the hybrid fillers, tribo‐tests were also done on composites filled with single CTBN, MoS2 and SiO2. It is revealed that the transfer of both the EP/CTBN matrix and SiO2@MoS2 CSs fillers play an important role in governing the tribo‐properties of rubber toughened EP composites. Depending on contacting conditions, the SiO2@MoS2 CSs fillers might be released into the sliding interface and tribo‐chemical reactions might take place, both of which helped improve the tribo‐properties of studied composites. [ABSTRACT FROM AUTHOR]

The rapid development of 4D printing provides a potential strategy for the fabrication of deployable medical devices (DMD). The minimally invasive surgery to implant the DMD into the body is critical, 4D printing DMD allows the well‐defined device to be implanted with a high‐compacted shape and transformed into their designed shape to meet the requirement. Herein, a 4D printing tissue engineering material is developed with excellent biocompatibility and shape memory effect based on the photocrosslinked polycaprolactone (PCL). The fast thiol‐acrylate click reaction is applied for photocrosslinking of the acrylates capped star polymer (s‐PCL‐MA) with poly‐thiols, that enable the 3D printing for the DMD fabrication. The cell viability, erythrocyte hemolysis, and platelet adhesion results indicate the excellent biocompatibility of the 4D printing polymer, especially the biological subcutaneous implantation results confirm the promote tissue growth and good histocompatibility. A 4D printing stent with deformable shape and recovery at a temperature close to human body temperature demonstrated the potential application as DMD. In addition, the everolimus is loaded to the polymer (ps1‐PCL) through host‐guest coordination with β‐cyclodextrin as the core of the star polymer, which shows sustained drug release and improved body's inflammatory response. [ABSTRACT FROM AUTHOR]

Self‐rolling allows the bilayer to transform into a 3D structure in response to specific external stimulation, such as heat, humidity, ions, etc. Herein, we report a 4D printing bilayer with a top sodium alginate layer and bottom polycaprolactone layer that could be rolled up to a tubular structure upon exposure to heat and Ca2+ solution stimulation. The discrepancy in the swelling and thermal‐responsiveness between alginate and polycaprolactone induced the self‐rolling under different stimuli. The self‐rolling behavior of the bilayer depends on the aspect ratio, thickness ratio of the bilayer film, the pattern, and external stimuli. Thus, a tailorable surface of the self‐rolled tube was obtained by tuning the bilayer parameter and the stimuli medium to meet varied demands. This controllable shape changing provides a strategy for the preparation of well‐defined tubular structures. Besides, the biocompatibility of bilayer film suggests the potential application in the field of biomedical device such as vascular stent. [ABSTRACT FROM AUTHOR]

In this article, thermosetting polyimide (TPI) composites based on two ideal ingredients (graphite/graphene‐like carbon nitride, g‐C3N4) were designed with different fibers and their tribological performance was comprehensively investigated at different high temperatures. It was found that the synergistic effect between solid lubricants graphite blended with g‐C3N4 and reinforced fibers on friction and wear performance. Extremely lower friction and wear behavior of TPI composite is attained with aramid pulps (APs) at high temperatures. More importantly, an obvious transition of wear rate and friction took place with aramid pulps under 200°C. When the cross‐sections of the transfer films were analyzed using focused ion beam transmission electron microscopy (FIB‐TEM) and X‐ray photoelectron spectroscopy (XPS), it was found that graphite and g‐C3N4 combined with APs led to simultaneous improvement in load‐carrying capability of TPI matrix and durability of tribofilms subjected to complex physical and chemical reaction. Our work discloses a route for developing the TPI composite exposed to high temperatures with extremely lower friction and wear rate. [ABSTRACT FROM AUTHOR]