Solvent Content Controlling Strategy for Cocrystallizable Polyesters Enables a Stress-Free Two-Way Shape Memory Effect with Wider Service Temperatures.

It is challenging to enhance the stress-free two-way shape memory (stress-free TWSM) effect to obtain a wide range of response temperatures. Herein, a polycaprolactone (PCL)/poly(ω-pentadecalactone) (PPDL) is photocured under UV light irradiation in the solvent of 1,1,2-trichloroethane (TCA), to obtain a series of cross-linked polyesters (CPES). Controlling solvent content (SC) which is removed after the polymerization allows the yielded CPES to perform a regulatable thermodynamic and stress-free TWSM properties. High SC is beneficial to reduce the degree of chain overlap (C/C* ) of PPDL chain segments in the PCL-based CPES network, then causes the cocrystallization of PCL and PPDL and yielding an additional melting-transitions (Tm ). An enhanced stress-free TWSM is obtained in high SC samples (CPES-15-90), reflected in the attainment of a wide range of response temperature, which means a wider service temperature. The enhancement is reflected in higher reversible strain of high SC samples compared with the samples prepared with low SC when varying high trigger temperature (Thigh ). Even at high Thigh , the high SC sample still has reversible strain. Therefore, controlling SC strategy for photocuring copolyester not only provides a new preparation approach for high-performance shape memory (SM) polymers, but also offers new condensed polymer structure to explore.

Supramolecular Oleogel-Impregnated Macroporous Polyimide for High Capacity of Oil Storage and Recyclable Smart Lubrication.

Developing smart lubrication materials to achieve recyclable and durable lubrication and excellent wear resistance under various running conditions has great significance in fields ranging from aerospace to advanced engineering machinery but has proven challenging. Herein, a supramolecular oleogel with reversible gel-to-liquid transition was impregnated into macroporous polyimide (MPPI-gel) to obtain a smart lubrication material, which exhibited recyclable smart lubrication with an enhanced oil content and oil retention. The self-assembly of the gelator in polyalphaolefin10 (PAO10) formed three-dimensional networks that encapsulated the PAO10 during the service process, and the MPPI-gel could exhibit a high oil retention (approximately 99%). The gel-to-liquid transition allows the lubricant to be extruded and transferred to the surface of the macroporous matrix (MPPI) under thermal-mechano-stimuli and vice versa. The extruded lubricant can be sucked back into the MPPI pores through the capillary force and recovered to the oleogel when removing the external stimuli. Due to the high oil content, high oil retention, and recyclable lubricant releasing/reabsorbing, MPPI-gel exhibited recyclable smart lubrication (at least 1852 cycles; each cycle lasted for 1 h), a stable coefficient of friction (∼0.06) under alternating conditions (the frequency varied from 1 to 20 Hz, and the load varied from 10 to 46 N), and long-term conditions (at least 10 days). Therefore, MPPI-gel holds the promise of realizing smart lubrication according to the external stimuli with both high oil storage and recyclable lubricant releasing/reabsorbing with the porous matrix.

Increased crop water requirements have exacerbated water stress in the arid transboundary rivers of Central Asia.

Water scarcity and ecological degradation as a result of the expansion of irrigated agriculture in arid regions have become global issues. A better understanding of the changes in crop water requirements (CWRs) is important for promoting sustainable development, particularly the water resource management of transboundary rivers. In this study, the latest and complete meteorological station and crop area data, the CropWat model, and the slope method were used to estimate the CWR in the Syr Darya Basin (SDB) of Central Asia from 2000 to 2018. The spatiotemporal variation of the water requirements for primary crops at the city scale was first assessed. The impacts of climate and cultivated land change on the CWR were quantified, and the associated impacts of the CWR on the water resources and environment were discussed. The results revealed that the mean unit area CWR of the SDB was 944.1 mm and the rate of increase was 7.6 mm/a from 2000 to 2018. The area of the primary crops expanded by 5851.6 km2, and the total CWR increased at a mean rate of 2.0 × 108 m3/a, with the majority of this change being concentrated between 2010 and 2018. By 2018, the total CWR reached 194.8 × 108 m3. The lower reaches of the SDB were associated with a high CWR and a high rate of increase. Along with the reduction in basin water resources, the increased CWR has exacerbated the water stress in the SDB. Sensitivity analysis indicated that the dominant factors influencing the change in the CWR are cultivated land change (65.0%) and climate change (35.0%). Owing to a reasonable crop planting structure, the middle reaches maintained a relatively low CWR and rate of increase. Given the predicted changes in climate, optimizing crop planting structure and controlling the expansion of cultivated land in order to reduce the CWR can help to mitigate water scarcity.