Vapor‐Triggered Mechanical Actuation in Polymer Composite Films Based on Crystalline Organic Cages

Abstract

The fabrication of smart materials, which can efficiently mimic biological systems through the introduction of soft components, is of great importance in the emerging fields of sensors and actuators. Herein, a smart composite film that can mechanically respond to vapors trigger then readily restores its original shape upon the removal of the stimuli is reported. This actuating composite film was prepared by mixing the highly elastic poly (vinylidene fluoride) (PVDF) polymer with the flexible and crystalline organic cages (Oba‐cage) at variable concentrations. The mechanism of the mechanical response could be accurately recorded due to the ordered cage crystals. This work highlights the importance of designing smart materials at the molecular level to precisely control the response or reaction upon the introduction of different triggers, which can ultimately lead to a monumental leap in the field of soft robotics.

Tunable Crystalline Organic Cage for Selective Sorting of Ortho-Monohalotoluene Isomers

“…Oba-cage was synthesized through a one-step condensation reaction of flexible 4,4′-oxybisbenzaldehyde with flexible tris­(2-aminoethyl) amine (TREN) in acetonitrile with excellent 82% yield (Scheme S1). Proton, 13 C NMR and ESI mass spectra results confirmed the successful synthesis of Oba-cage (Figures S1 and S2). It is noteworthy to mention that the presence of oxygen between the two phenyl rings in Oba-cage breaks the conjugation of the two halves and presents some degree of conformational flexibility when compared to the two examples earlier mentioned above. ,, Two different crystals Oba-cage@THF and Oba-cage@CHCl 3 were obtained when Oba-cage was crystallized separately by diffusion of n -hexane into its THF and Chloroform solutions respectively (Figure S3 and Table S1).…”

“…In this present study, we corroborate that using materials with fixed shape or pore size may not be a prerequisite to achieve excellent separation performance, but structural dynamism and flexibility of the materials can be remarkable properties for such separation. − Herein we investigate a more flexible oxybis-benzaldehyde-based imine cage ( Oba-cage ) and test its capacity to separate a larger monohalotoluene isomers (Scheme ). Oba-cage could separate ortho-chlorotoluene (oCT) and ortho-bromotoluene (oBT) from 1:1 (v/v) mixtures of their isomers with 70.9% and 93.4% purity, respectively, but shows about 51.7% purity for ortho-fluorotoluene (oFT) isomer.…”

“…As earlier reported by our group, the role of the structural flexibility of Oba-cage in inclusion of different organic solvents in the extrinsic voids in the crystal packing irrespective of their sizes has been discussed by considering and comparing the crystal structures of Oba-cage@CHCl 3 and Oba-cage@oCT . This is possible because they both crystallized in the same crystal system and space group with the inclusion of their respective solvents (Figures S3 and S9).…”

“…The persistent inclusion of the chlorinated solvents between the cages in the crystal structure of Oba-cage after several trials even when the crystals were grown in DCM prompted the investigation of the material for the uptake/separation of monochlorotoluene and by extension the other monohalotoluene isomers (fluorotoluene and bromotoluene) (Scheme ). Like some other reported (2 + 3) organic cages, the solvents of crystallization are not included within the cage but instead are located between the cages. ,, …”

“…This is possible because they both crystallized in the same crystal system and space group with the inclusion of their respective solvents (Figures S3 and S9). These structural changes appear therefore to favor the discrimination of only ortho shape isomers from their corresponding monohalotoluene isomers, and this can be attributed in part to the formation of shape induced host/guest hydrogen bonding intermolecular interactions (C–H···Cl, C–H···π, etc.) as seen in Oba-cage@oCT crystal structure.…”