Large-Area Layered Membranes with Precisely Controlled Nano-Confined Channels.

Two-dimensional (2D) nanosheets-based membranes, which have controlled 2D nano-confined channels, are highly desirable for molecular/ionic sieving and confined reactions. However, it is still difficult to develop an efficient method to prepare large-area membranes with high stability, high orientation, and accurately adjustable interlayer spacing. Here, we present a strategy to produce metal ion cross-linked membranes with precisely controlled 2D nano-confined channels and high stability in different solutions using superspreading shear-flow-induced assembly strategy. For example, membranes based on graphene oxide (GO) exhibit interlayer spacing ranging from 8.0 ± 0.1 Å to 10.3 ± 0.2 Å, with a precision of down to 1 Å. At the same time, the value of the orientation order parameter (f) of GO membranes is up to 0.95 and GO membranes exhibit superb stability in different solutions. The strategy we present, which can be generalized to the preparation of 2D nano-confined channels based on a variety of 2D materials, will expand the application scope and provide better performances of membranes.

Dynamic-Bond-Mediated Chain Reptation Enhances Energy Dissipation of Elastomers.

Vibrations with various frequencies in daily life and industry can cause health hazards and fatigue failure of critical structures, which requires the development of elastomers with high energy dissipation at desired frequencies. Current strategies relying on tuning characteristic relaxation time of polymer chains are mostly qualitative empirical methods, and it is difficult to precisely control damping performances. Here, we report a general strategy for constructing dynamic crosslinked polymer fluid gels that provide controllable ultrahigh energy dissipation. This is realized by dynamic-bond-mediated chain reptation of polymer fluids in a crosslinked network, where the characteristic time of chain reptation is dominated by the presence of well-defined dissociation time of dynamic bonds and almost independent of their molar mass. Using prototypical supramolecular polydimethylsiloxane elastomers, we demonstrate that dynamic crosslinked polymer fluid gels exhibit a controllable ultrahigh damping performance at desired frequencies (10-2~102 Hz), exceeding that of typical state-of-the-art silicone damping materials. Their shock absorption is over 300 % higher than that of commercial silicone rubber under the same impact force.

Habitat-specific regulation of bacterial community dynamics during phytoplankton bloom succession in a subtropical eutrophic lake.

Phytoplankton blooms, an important indicator of severe eutrophication, are a globally significant consequence of anthropogenic activities and climate change on freshwater lakes. Shifts in microbial communities during phytoplankton blooms have been extensively investigated, yet we have a limited understanding of how distinct assembly processes underlying the temporal dynamics of freshwater bacterial communities within different habitats respond to the succession of phytoplankton blooms. To address this knowledge gap, we collected both water and sediment samples in a subtropical eutrophic lake over a complete period of phytoplankton blooms to assess the dynamics of bacterial communities and the temporal shifts in assembly processes. Our results showed that phytoplankton blooms strongly altered the diversity, composition, and coexistence patterns of both planktonic and sediment bacterial communities (PBC and SBC), but the successional patterns differed between PBC and SBC. PBC were less temporally stable under bloom-induce disturbances, with higher variations in temporal dynamics and greater sensitivity to environmental fluctuations. Furthermore, the temporal assembly patterns of bacterial communities in both habitats were mainly driven by homogeneous selection and ecological drift. In the PBC, the role of selection decreased over time, while ecological drift became increasingly important. Conversely, in the SBC, the relative impact of selection and ecological drift on community assemblages fluctuated less over time, with selection remaining the dominant process throughout the bloom.

Large-Area Ultrastrong and Stiff Layered MXene Nanocomposites by Shear-Flow-Induced Alignment of Nanosheets.

To shield increasingly severe radiation pollution, ultrathin MXene-based electromagnetic interference (EMI) shielding materials with excellent mechanical properties are urgently demanded in wearable electrical devices or aerospace fields. However, it is still a challenge to fabricate ultrastrong and stiff MXene-based nanocomposites with excellent EMI shielding capacity in a universal and scalable manner. Here, inspired by the natural nacre structure, we propose an efficient superspreading strategy to construct a highly oriented layered "brick-and-mortar" structure using shear-flow-induced alignment of MXene nanosheets at an immiscible hydrogel/oil interface. A continuous and large-area MXene nanocomposite film has been fabricated through a homemade industrial-scale continuous fabrication setup. The prepared MXene nanocomposite films exhibit a tensile strength of 647.6 ± 56 MPa and a Young's modulus of 59.8 ± 6.1 GPa, respectively. These outstanding mechanical properties are attributed to the continuous interphase layer that formed between the well-aligned MXene nanosheets. Moreover, the obtained MXene nanocomposites also show great EMI shielding effectiveness (51.6 dB). We consider that our MXene-based nanocomposite films may be potentially applied as electrical or aerospace devices with superior mechanical properties and high EMI shielding capacity.

High-performance poly(acrylic acid) hydrogels formed with a block copolymer crosslinker containing amino-acid derivatives.

Two block copolymers containing two amino-acid derivatives, PEO-b-PLAA and PEO-b-PAAC, were fabricated through atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer polymerization (RAFT). Then, they were employed as a macro-crosslinker to prepare high-performance poly(acrylic acid) (PAA) hydrogels named "PxAy" or "TyAz". There were numerous synergistic noncovalent interactions with hydrogen bonds between the macro-crosslinker and PAA chains, as well as entanglement of polymer chains. Hence, the hydrogels exhibited desirable mechanical properties and self-healing abilities. For PxAy hydrogels, the maximum fracture elongation and fracture strength were 9800% and 120.01 kPa, respectively. Moreover, the enhanced physical interaction enabled the hydrogels to have rapid self-healing abilities without stimulation. The hydrogels showed >80% self-healing efficiency and exhibited ∼10-3 S cm-1 electrical conductivity upon the introduction of KCl. Meanwhile, benefitting from doubling the number of carboxyl groups in the macro-crosslinker of the TyAz hydrogels compared with the PxAy hydrogels, the mechanical properties of TyAz hydrogels could be promoted further and notch-insensitivity could be observed. Tough, adhesive, self-healable, and conductive PAA hydrogels with different structures of amino-acid derivatives could aid the development of macro-crosslinkers.