Self-healing polymers
with microphase-separated structure are plagued
with inferior self-healing efficiency at room temperature due to a
lack of dynamic interactions in hard domains. Herein, we describe
a novel strategy of multiphase active hydrogen bonds (H-bonds), toward
realizing fast and efficient self-healing at room temperature, even
under harsh conditions. The core conception is to incorporate thiourea
moieties into microphase-separated polyurea network to form multistrength
H-bonds, which destroy the crystallization of hard domains and, at
the same time, insert the dynamic reversible H-bonds in both hard
and soft segments, accounting for the surprisingly self-healing performances.
The synthesized polymeric material, poly(dimethylsiloxane)–4,4′-methylenebis(phenyl
isocyanate)–1,1′-thiocarbonyldiimidazole, completely
recovers all of the mechanical properties within 4 h at room temperature
after rupture. Significantly, self-healing process can also take place
at low temperature (restoration with an 85% efficiency in 48 h at
−20 °C) or in the water (restoration with a 95% efficiency
in 4 h). Depending on the cleavage/reformation of multiphase H-bonds,
the material exhibits unprecedented ultrastrechability and notch-insensitiveness.
It can be stretched up to 31 500% without fracture and reach
a notch-insensitive stretching of up to 18 000%. These exceptional
characteristics inspired us to fabricate highly stretchable self-healable
underwater conductor and protective self-healing film for suppressing
shuttling of polysulfides and preventing crack propagation in S cathode,
which provide the pathway for applications in underwater electronic
devices or advanced Li–S batteries.
A simple and straightforward strategy was developed to fabricate magnetically separable MnFe 2 O 4 Àgraphene photocatalysts with differing graphene content. It was found that graphene sheets were fully exfoliated and decorated with MnFe 2 O 4 nanocrystals having an average diameter of 5.65 nm and a narrow particle size distribution. It is very interesting that, although MnFe 2 O 4 alone is photocatalytically inactive under visible light irradiation, the combination of MnFe 2 O 4 nanoparticles with graphene sheets leads to high photocatalytic activity for the degradation of methylene blue under visible light irradiation. The strong magnetic property of MnFe 2 O 4 nanoparticles can be used for magnetic separation in a suspension system, and therefore it does not require additional magnetic components as is the usual case. Consequently, the MnFe 2 O 4 Àgraphene system becomes a dual function photocatalyst. The significant enhancement in photoactivity under visible light irradiation can be ascribed to the reduction of graphene oxide (GO), because the photogenerated electrons of MnFe 2 O 4 can transfer easily from the conduction band to the reduced GO, effectively preventing a direct recombination of electrons and holes. Hydroxyl radicals play the role of main oxidant in the MnFe 2 O 4 Àgraphene system, and the radicals' oxidation reaction is obviously dominant.
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