Nanosheet-Filled Polymer Film from Flow-Induced Coassembly: Multiscale Structure Visualization and Application.

The nanoplatelet-filled polymer composite (NFPC) materials have received increasing attention because of their high strength-to-weight ratio and toughness. However, high-performance NFPC materials still face many challenges: (1) how to transfer the intrinsic extraordinary performance of individual nanoplatelets into highly ordered macroscale bulk materials; (2) how to obtain a strong interface bonding between polymer and nanoplatelet filler; and (3) how to truly reflect the structure of NFPC film. Here, to address these problems, the flow-induced assembly method is employed to fabricate the large-size continuous, flexible, highly oriented, and transparent NFPC film. During flow-induced orientation, nanoplatelet and polymer can be coassembling together to form a highly ordered layered structure with dozens of layers. On the other hand, the layered double hydroxide (LDH) nanosheet filler with single layer and abundant hydroxyl sites is prepared to strengthen interface by forming hydrogen bonds with polymers. To explore the effect of multiscale structure on property, carbon dots (CDs) are introduced to light up the inorganic nanoplatelet. By fixing and confining CDs in a rigid environment, the CD-LDH-based composite film shows excellent dual emission characteristics, which can be used to evaluate gas barrier, humidity, and temperature with direct visualization, high sensitivity, and easy to operation.