No abstract

Wearable electronics with healability have been extensively researched recently. To provide wearing comfort, fabrics are often adopted as the base materials. Intrinsic healability, however, is challenging for fabrics because of the inability to retain the fibrous morphologies. Herein, an unprecedented strategy is presented for producing electrospun fabrics that are intrinsically healable by carefully balancing the crystalline structural support and healing ability. Fluorocarbon polymers with different crystallinities are mixed with ionic liquids to form ionogels, which are spun into fabrics using a unique wet electrospinning apparatus. Importantly, the introduction of the crystalline domains prevents the fusion of the electrospun fibers; even after 1 year, no significant morphological change is observed. The nonwoven fabrics are not only stretchable and waterproof but also intrinsically healable. The ion–dipole interactions between the polar copolymers and ionic liquids provide the reversible physical crosslinking essential to the healing capability. When damaged, the fabrics can be overlapped and healed after applying pressure. Moreover, the fabrics demonstrate healability underwater. Healable sensing devices, pressure, and tensile sensors are also designed by printing ion‐conductive gels as electrodes. Both devices show good stability before and after healing. This work demonstrates the first example of intrinsically healable electrospun fabrics, which are promising for fabric‐based wearable electronics and smart clothing.

Untethered small actuators have drawn tremendous interest owing to their reversibility, flexibility, and widespread applications in various fields. For polymer actuators, however, it is still challenging to achieve programmable structural changes under different stimuli caused by the intractability and single-stimulus responses of most polymer materials. Herein, multi-stimuli-responsive polymer actuators that can respond to light and solvent via structural changes are developed. The actuators are based on bilayer films of polydimethylsiloxane (PDMS) and azobenzene chromophore (AAZO)-crosslinked poly(diallyldimethylammonium chloride) (PDAC). Upon UV light irradiation, the AAZO undergoes trans-cis-trans photoisomerization, causing the bending of the bilayer films. When the UV light is off, a shape recovery toward an opposite direction occurs spontaneously. The reversible deformation can be repeated at least 20 cycles. Upon solvent vapor annealing, one of the bilayer films can be selectively swollen, causing the bending of the bilayer films with the directions controlled by the solvent vapors. The effects of different parameters, such as the weight ratios of AAZO and film thicknesses, on the bending angles and curvatures of the polymer films are also analyzed. The results demonstrate that multi-stimuli-responsive actuators with fast responses and high reproducibility can be fulfilled.

Over the past few decades, stimuli-responsive materials have been widely applied to porous surfaces. Permeability and conductivity control of ions confined in nanochannels modified with stimuli-responsive materials, however, have been less investigated. In this work, the permeability and conductivity control of ions confined in nanochannels of anodic aluminum oxide (AAO) templates modified with thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes are demonstrated. By surface-initiated atom transfer radical polymerization (SI-ATRP), PNIPAM brushes are successfully grafted onto the hexagonally packed cylindrical nanopores of AAO templates. The surface hydrophilicities of the membranes can be reversibly altered because of the lower critical solution temperature (LCST) behavior of the PNIPAM polymer brushes. From electrochemical impedance spectroscopy (EIS) analysis, the temperature-gating behaviors of the AAO-g-PNIPAM membranes exhibit larger impedance changes than those of the pure AAO membranes at higher temperatures because of the aggregation of the grafted PNIPAM chains. The reversible surface properties caused by the extended and collapsed states of the polymer chains are also demonstrated by dye release tests. The smart thermo-gated and ion-controlled nanoporous membranes are suitable for future smart membrane applications.[a] M.

Regular arrays of anisotropic polymer nanomaterials have attracted great attention because of their unique properties and various applications such as solar cell devices, sensors, and supercapacitors. The control of the shape manipulation and tailored properties of individual polymer nanomaterials in arrays, however, remains a great challenging task. In this work, we demonstrate a versatile approach to fabricate elliptical and bent polymer nanorod arrays through laser-induced photo-fluidization of azobenzene-containing polymers (azopolymers). Ordered anodic aluminum oxide (AAO) membranes are used as templates for generating azopolymer nanorod arrays via a solvent vapor annealing-induced wetting method. After being released from the AAO templates and shone by linearly polarized lights, the nanorod arrays can be transformed into anisotropic nanostructures, driven by the trans-to-cis and cis-to-trans isomerization of the azobenzene groups in the azopolymers. Depending on whether the laser beam is shone at normal or tilt angles of incidence, elliptical or bent nanorod arrays can be prepared, respectively. The deformation degrees and water wettabilities of the nanorod arrays can be varied by changing the illumination times. This study reports a beneficial route to prepare ordered arrays of anisotropic polymer nanostructures for advanced applications.