Living matter has the ability to perceive multiple stimuli and respond accordingly. However, the integration of multiple stimuli-responsiveness in artificial materials usually causes mutual interference, which makes artificial materials work improperly. Herein, we design composite gels with organic‒inorganic semi-interpenetrating network structures, which are orthogonally responsive to light and magnetic fields. The composite gels are prepared by the co-assembly of a photoswitchable organogelator (Azo-Ch) and superparamagnetic inorganic nanoparticles (Fe3O4@SiO2). Azo-Ch assembles into an organogel network, which shows photoinduced reversible sol-gel transitions. In gel or sol state, Fe3O4@SiO2 nanoparticles reversibly form photonic nanochains via magnetic control. Light and magnetic fields can orthogonally control the composite gel because Azo-Ch and Fe3O4@SiO2 form a unique semi-interpenetrating network, which allows them to work independently. The orthogonal photo- and magnetic-responsiveness enables the fabrication of smart windows, anti-counterfeiting labels, and reconfigurable materials using the composite gel. Our work presents a method to design orthogonally stimuli-responsive materials.
Microcapsules (Mic-MBP) based on the melamine borate coated red phosphorus (RP) were prepared, and its synergistic flame retardant with zinc borate (ZB) on polyethylene (PE) was investigated. The flame retardant properties of the PE/20% Mic-MBP/10%ZB were superior to that of PE/20%RP/10%ZB. Furthermore, the limiting oxygen index of PE/20%Mic-MBP/10%ZB was 25.2%, and PE/20%Mic-MBP/10%ZB reached the UL-94V-0 rating. Compared with PE, the peak heat release rate (pk-HRR), total heat release (THR) and average effective heat of combustion (av-EHC) of PE/20%Mic-MBP/10%ZB had decreased. In addition, the flame retardant mechanism was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) and Fourier transform infrared spectroscopy (FT-IR). The results showed that the residual char of PE/20%Mic-MBP/10%ZB had thermal stability, and the formation of phosphorus free radicals and nonflammable gases effectively reduced the burning intensity of the gas phase. It indicated that Mic-MBP/ZB showed a condensed and gas phase flame retardant effect.
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