It is highly desirable, although very challenging, to develop self‐healable materials exhibiting both high efficiency in self‐healing and excellent mechanical properties at ambient conditions. Herein, a novel Cu(II)–dimethylglyoxime–urethane‐complex‐based polyurethane elastomer (Cu–DOU–CPU) with synergetic triple dynamic bonds is developed. Cu–DOU–CPU demonstrates the highest reported mechanical performance for self‐healing elastomers at room temperature, with a tensile strength and toughness up to 14.8 MPa and 87.0 MJ m−3, respectively. Meanwhile, the Cu–DOU–CPU spontaneously self‐heals at room temperature with an instant recovered tensile strength of 1.84 MPa and a continuously increased strength up to 13.8 MPa, surpassing the original strength of all other counterparts. Density functional theory calculations reveal that the coordination of Cu(II) plays a critical role in accelerating the reversible dissociation of dimethylglyoxime–urethane, which is important to the excellent performance of the self‐healing elastomer. Application of this technology is demonstrated by a self‐healable and stretchable circuit constructed from Cu–DOU–CPU.
A simple
preparation process was developed for magnetic nanoparticles, consisting
of chitosan coated on Fe3O4 nanoparticles, to
be used as support for enzyme immobilization. Cellulase was covalently
immobilized on this magnetic support using glutaraldehyde as a coupling
agent. The structure, morphology, and magnetic property of the support
were studied by X-ray diffraction, vibrating-sample magnetometer,
thermogravimetric analysis, transmission electron microscopy, and
Fourier transform infrared (FT-IR) spectroscopy. The properties of
the immobilized cellulase were investigated by regarding activity,
optimum operational pH and temperature, thermal stability, and reusability.
The amount of cellulase on the nanoparticles reached 112.3 mg/g. The
characterization and determination results showed that the immobilized
cellulase had higher operational stability than the free enzyme over
wider temperature and pH ranges and good reusability after recovery
by magnetic separation. Therefore, these magnetic Fe3O4–chitosan nanoparticles are expected to be a useful
support for enzyme.
The superparamagnetic multilayer hybrid hollow microspheres have been fabricated using the layer-by-layer assembly technique by the electrostatic interaction between the polyelectrolyte cation chitosan (CS) and the hybrid anion citrate modified ferroferric oxide nanoparticles (Fe 3 O 4 -CA) onto the sacrificial polystyrene sulfonate microspheres templates after etching the templates by dialysis. The saturation magnetization and magnetite contents of the superparamagnetic multilayer hybrid hollow microspheres were 32.46 emu/g and 51.3%, respectively. The hybrid hollow microspheres showed pH-sensitive characteristics. The adsorption and release of the basic dye (methylene blue) were applied to investigate the interaction between the amino groups of CS and the carboxyl groups of the Fe 3 O 4 -CA nanoparticles in different pH media. The superparamagnetic pH-sensitive multilayer hybrid hollow microspheres are expected to be used for the targeted controlled release of drugs or in diagnostics. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3135-3144, 2010 KEYWORDS: hybrid hollow microspheres; layer-by-layer assembly; pH sensitive; superparamagnetic; targeted controlled releaseRecently, surface-charged nanoparticles have been used for the fabrication of the multilayer hybrid hollow microspheres.
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