One-pot preparation and applications of self-healing,self-adhesive PAA-PDMS elastomers

A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.

Excellentπ-Bowl Semiconductors Based on C_(70)Subunit

As open substructures of fullerenes,aromaticπ-bowls are promising candidates as new organic semiconductors,as well as attractive hosts for fullerenes.We demonstrate herein the synthesis and characterization of a novel C_(2v)symmetricπ-bowl,pyracyleno[6,5,4,3,2,1-pqrstuv]pentaphene(3).Bowl 3 was equipped with two distinctive reactive sites,allowing for bromination and cross-coupling reactions to readily yield functionalized bowls with two 2,4,6-trimethylphenyl(5)and triethylsilyl(TES)-ethynyl(6)substituents,respectively.Variable-temperature 1H NMR analysis and density functional theory(DFT)calculations indicated bowl-to-bowl inversions of 3,5,and 6 at room temperature.By alternating the substituents,the crystal structures of the threeπ-bowls 3,5,and 6 could be controlled from 1D linear to 1D slipped to 2D herringbone packing motifs,providing insight into the packing behavior ofπ-bowls.1H NMR titration study indicated that the TES-ethynyl substituent enhanced the ability ofπ-bowl to bind C_(70)with an association constant of 2485 M−1.The C_(70)molecules withπ-bowls 3 and 6 formed 1:1 complexes,in which C_(70)molecules aggregated into zig-zag and 1D linear arrays,respectively.The hole mobility of 2.3 cm^(2)V^(−1)^s(−1)and electron mobility of 0.16 cm^(2)V^(−1)^s(−1)ofπ-bowl 3 and its complex with C_(70)were demonstrated,respectively,which proved a great value for the development of aromaticπ-bowl semiconductors with tunable properties for organic electronic devices.

Visible-Light-Responsive Crystalline Solids by Equipping Covalent Organic Frameworks with Donor-Acceptor Stenhouse Adducts

Controlling properties of crystalline solids by light remains a challenge because the lack of intrinsic structural flexibility limits the necessary molecular mobility for photoisomerization. In this work, we reported a series of visible-light-responsive covalent organic frameworks (COFs) by introducing donor-acceptor Stenhouse adducts (DASAs) with various electron-withdrawing moieties via a post-modified strategy. The DASAs-functionalized COFs exhibit distorted honeycomb layered topology with long-range periodicity. The DASAs grafted on the skeletons are pointing into the nanopores of COFs, which weakens intermolecular aggregation and ensures sufficient free volume to undergo reversible isomerization between linear and cyclic states. Furthermore, the crystalline and optical properties of COFs as well as the geometrical size and hydrophilicity inside the nanopores were reversibly controlled by alternating visible light irradiation and heat. Finally, methyl violet was used as the cargo molecules to be immobilized into the nanopores of COFs, which showed fast release under controlling of visible light.

Learning from Spiropyrans:How to Make Further Developments of Donor-Acceptor Stenhouse Adducts

Donor-acceptor Stenhouse adducts(DASAs)as a species of novel photochromic molecules,have been developing rapidly and attracting broad researchers’sights since 2014.DASAs show visible/near-infrared(NIR)light induced linear-to-cyclic isomerization and heat induced cyclic-to-linear isomerization,therefore they are attractive in photoresponsive hydrogels,drug delivery,cell culturing and tissue engineering.As a series of well-known photoresponsive molecules,spiropyrans(SPs)show similar molecular properties and comparable photoswitching with DASAs.UV light triggers closed-to-open(also known as spirocyclic(SC)-to-merocyanine(MC))isomerization of SPs,while the reversed open-to-closed isomerization occurs under visible light or heat.Light irradiation switches the molecular color,scale,geometry,and polarity of SPs and DASAs reversibly.Since the researches on DASAs are still in the infancy,the chemical structures,isomerization mechanisms and potential applications need to be further investigated and explored.The well-studied SPs have important reference values to the comprehensive developments of DASAs.In the present review,we summarized,compared and discussed SPs and DASAs with regards to their molecular structures,synthesis,photoswitching and applications.We also make our perspective on the developments of DASA in future.