Weldable and closed-loop recyclable monolithic dynamic covalent polymer aerogels

Owing to their low density, high porosity and unique micro-nanostructures, aerogels are attractive for application in various fields; however, they suffer from shrinkage and/or cracking during preparation, mechanical brittleness, low production efficiency and non-degradation. Herein, we introduce the concept of dynamic covalent polymer chemistry to produce a new class of aerogels&mdash;referred to as DCPAs. The resulting lightweight DCPAs have the potential to be prepared on a large scale and feature high porosity (90.7%&ndash;91.3%), large degrees of compression (80% strain) and bending (diametral deflection of 30 mm) without any cracks, as well as considerable tensile properties (an elongation with a break at 32.7%). In addition, the DCPAs showcase the emergent characteristics of weldability, repairability, degradability and closed-loop recyclability that are highly desirable for providing versatile material platforms, though hardly achieved by traditional aerogels. Taking advantage of their robust porous structures, we demonstrate the potential of DCPAs for applications in thermal insulation and emulsion separation. These findings reveal that the dynamic covalent bond strategy would be generalized for the production of a new generation of aerogels with customized features for functioning in the field of intelligent and sustainable materials. &nbsp;</p

The Overseeing Mother: Revisiting the Frontal-Pose Lady in the Wu Family Shrines in Second Century China

Located in present-day Jiaxiang in Shandong province, the Wu family shrines built during the second century in the Eastern Han dynasty (25–220) were among the best-known works in Chinese art history. Although for centuries scholars have exhaustively studied the pictorial programs, the frontal-pose female image situated on the second floor of the central pavilion carved at the rear wall of the shrines has remained a question. Beginning with the woman’s eyes, this article demonstrates that the image is more than a generic portrait (“hard motif ”), but rather represents “feminine overseeing from above” (“soft motif ”). This synthetic motif combines three different earlier motifs – the frontal-pose hostess enjoying entertainment, the elevated spectator, and the Queen Mother of the West. By creatively fusing the three motifs into one unity, the Jiaxiang artists lent to the frontal-pose lady a unique power: she not only dominated the center of the composition, but also, like a divine being, commanded a unified view of the surroundings on the lofty building, hence echoing the political reality of the empress mother’s “overseeing the court” in the second century during Eastern Han dynasty

Supramolecular Side-Chain Poly[2]pseudorotaxanes Formed by Orthogonal Coordination-Driven Self-Assembly and Crown-Ether-Based Host–Guest Interactions

The themes of coordination-driven self-assembly, host–guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]­pseudorotaxanes. Specifically, a bis­(<i>p</i>-phenylene)-34-crown-10 derivative <b>1</b> bearing two pyridyl groups polymerizes into a side-chain poly[2]­pseudorotaxane upon the addition of di-Pt­(II) acceptor <b>4</b> in the presence of paraquat. Interestingly, by adding a competitive guest <b>3</b>, the poly[2]­pseudorotaxane can realize a conversion in one pot

Supramolecular Side-Chain Poly[2]pseudorotaxanes Formed by Orthogonal Coordination-Driven Self-Assembly and Crown-Ether-Based Host–Guest Interactions

The themes of coordination-driven self-assembly, host–guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]­pseudorotaxanes. Specifically, a bis­(<i>p</i>-phenylene)-34-crown-10 derivative <b>1</b> bearing two pyridyl groups polymerizes into a side-chain poly[2]­pseudorotaxane upon the addition of di-Pt­(II) acceptor <b>4</b> in the presence of paraquat. Interestingly, by adding a competitive guest <b>3</b>, the poly[2]­pseudorotaxane can realize a conversion in one pot

Adjustable supramolecular polymer microstructures fabricated by the breath figure method

National Natural Science Foundation of China [20834004, 91027006]; Fundamental Research Funds for the Central Universities [2010QNA3008]; Zhejiang Provincial Natural Science Foundation of China [R4100009]; National Basic Research Program [2009CB930104]; State Key Laboratory of Supramolecular Structure and MaterialsHighly ordered supramolecular polymer honeycomb-patterned films were fabricated successfully via the static breath figure method. The supramolecular polymer that was used to prepare these intriguing films was obtained from the self-organization of a heteroditopic monomer based on the benzo-21-crown-7/secondary ammonium salt recognition motif. The morphologies of these microstructures were observed by scanning electron microscopy, optical microscopy and atomic force microscopy techniques. The monomer concentration plays an important role in the fabrication of these supramolecular polymer microstructures. The pore size of honeycomb-patterned films decreases with the increase of the monomer concentration from 4 wt% to 30 wt%. A microsphere (900 nm) pattern and a highly-ordered honeycomb-patterned film (2.0 mu m) were obtained via the static breath figure method using acetonitrile as the solvent at concentrations of 2 wt% and 30 wt%, respectively

Metallosupramolecular Poly[2]pseudorotaxane Constructed by Metal Coordination and Crown-Ether-Based Molecular Recognition

A novel bis­(<i>m</i>-phenylene)-32-crown-10 derivative bearing two π-extended pyridyl groups was synthesized, and its host–guest complexation with a paraquat derivative to form a threaded [2]­pseudorotaxane was studied. Subsequently, a poly[2]­pseudorotaxane was constructed with a metallosupramolecular polymer backbone via metal coordination, which was comprehensively confirmed by the combination of ¹H NMR, ³¹P­{¹H} NMR, DOSY NMR, DLS, and EDX techniques

Chemically-Responsive Complexation of A Diquaternary Salt with Bis(<i>m</i>‑phenylene)-32-Crown-10 Derivatives and Host Substituent Effect on Complexation Geometry

A chemically responsive diquaternary salt with π-extended surface was made. The host–guest complexation with chemo-responsiveness between three bis(<i>m</i>-phenylene)-32-crown-10 (BMP32C10) derivatives and this diquaternary salt guest was studied through the sequential addition of basic and acidic reagents (diethylamine and trifluoroacetic acid, respectively). Furthermore, the host-substituent effect on the complexation geometries of these three host–guest complexes, from taco to taco-type threaded to threaded structures by changing the substituent on BMP32C10 as shown by crystal structures, was also addressed

Benzo-21-Crown-7/Secondary Ammonium Salt [2]Rotaxanes with Fluoro/Chlorocarbon Blocking Groups

Three threaded structures capped by fluoro/chlorocarbon blocking groups with different sizes were constructed by template synthesis based on the benzo-21-crown-7/secondary ammonium salt recognition motif, as confirmed by ¹H NMR, electrospray mass spectrometry and single crystal X-ray analysis. The transformation from a rotaxane-like entity into a rotaxane was achieved by replacing the end group from the trifluoroacetic ester group to its trichloroacetic ester analogue

Chemically-Responsive Complexation of A Diquaternary Salt with Bis(<i>m</i>‑phenylene)-32-Crown-10 Derivatives and Host Substituent Effect on Complexation Geometry

A chemically responsive diquaternary salt with π-extended surface was made. The host–guest complexation with chemo-responsiveness between three bis(<i>m</i>-phenylene)-32-crown-10 (BMP32C10) derivatives and this diquaternary salt guest was studied through the sequential addition of basic and acidic reagents (diethylamine and trifluoroacetic acid, respectively). Furthermore, the host-substituent effect on the complexation geometries of these three host–guest complexes, from taco to taco-type threaded to threaded structures by changing the substituent on BMP32C10 as shown by crystal structures, was also addressed