Flexible and wearable sensor based on nanocomposite hydrogels has been proposed for monitoring the human large-scale, small-scale movements and several physiological signals. The nanocomposite hydrogel, prepared from graphene oxide (GO), polyvinyl alcohol (PVA) and polydopamine (PDA), exhibits excellent mechanical and electrical properties with tensile stress of 146.5 KPa, fracture strain of 2580%, fracture energy of 2390.86 KJ m−3, and the conductivity of 5 mS cm−1. In addition, it possesses other merits including good self-healing with the electrical self-healing efficiency of 98% of its original resistance within 10 s, and strong self-adhesion onto a variety of surfaces of materials. This self-adhesive, self-healing, graphene-based conductive hydrogel can further assembled as wearable sensors to accurate and real-time detect the signals of human large-scale motions (including bending and stretching fingers joints, wrists joints, elbows joints, neck joints and knees joints) and small-scale motions (including swallowing, breathing and pulsing) through fracturing and recombination of reduced graphene oxide (rGO) electrical pathways in porous structures of hydrogel networks. Furthermore, the hydrogel can also be used as self-adhesive surface electrodes to detect human electrophysiological (ECG) signals. Therefore, the hydrogel-based wearable sensor is expected to be used for long-term and continuous monitoring human body motion and detecting physiological parameters.
During the past few decades, the study of the single polymer chain has attracted considerable attention with the goal of exploring the structure-property relationship of polymers. It still, however, remains challenging due to the variability and low atomic resolution of the amorphous single polymer chain. Here, we demonstrated a new strategy to visualize the single metallopolymer chain with a hexameric or trimeric supramolecule as a repeat unit, in which Ru(II) with strong coordination and Fe(II) with weak coordination were combined together in a stepwise manner. With the help of ultrahigh-vacuum, low-temperature scanning tunneling microscopy (UHV-LT-STM) and scanning tunneling spectroscopy (STS), we were able to directly visualize both Ru(II) and Fe(II), which act as staining reagents on the repeat units, thus providing detailed structural information for the single polymer chain. As such, the direct visualization of the single random polymer chain is realized to enhance the characterization of polymers at the singlemolecule level.
Spider silk has received increased attention because of its high strength, good flexibility and adhesiveness. Herein we demonstrate a simple method to fabricate one type of flexible, multi-functional hydrogel fiber...
Ion-containing polymers
are of great importance for its unique structure and properties. An
ion-containing polyamide 6 (PA6) was prepared by grafting an ionic
liquid, 1-vinyl-3-butyl imidazole chloride [VBIM][Cl], onto the main
chain of PA6 using radiation-induced grafting. The grafted ions on
the PA6 main chain significantly influenced the structure and properties
of the PA6 matrix. The ions form nanoscale aggregations without inducing
further microphase separation. Acting as a physical “cross-linking
point,” each aggregation enhanced inter/intrachain interactions,
which increased the viscosity, storage modulus, and relaxation time
and reduced the ability of PA6 to crystallize. However, the bulky
cations of the grafted ionic liquid can also be seen as “spacers,”
which enlarge the distance among chains and reduce the strength of
the hydrogen bonds inherently existing in the PA6 matrix. The “cross-linking
points” and “spacers” of ions as well as the
hydrogen bonds of PA6 take effect collectively in the system. Moreover,
the ion-containing PA6 retains good melt processability compared with
PA6, despite increased viscosity, and can be easily melt-spun into
fibers. Fibers prepared from ion-containing PA6 showed improved mechanical
properties and antistatic performance and exhibited the expected antibacterial
properties, especially with regard to Escherichia coli. Inspiringly, covalently bonding ions to the PA6 main chain offers
a new strategy for fabricating functional fibers with permanent antistatic
and antibacterial properties.
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