Oscillatory shear induced gelation of graphene-poly(vinyl alcohol) composite hydrogels and rheological premonitor of ultra-light aerogels

Time evolution of 3-D structure of GO hydrogels was explored by rheological measurements. We showed that the GO hydrogels were thickened drastically by oscillatory shear flow if and only if both the angular frequencies and shear strain are small. We also showed that the plateau modulus (GN′) of GO hydrogels is rheological premonitory of ultra-light aerogels. The ultra-light aerogel fabricated in this work exhibited low density of 4.0 mg/cm3, low surface resistivity of 6.6 Ω/sq, high specific area of 1069 m2/g, and high recoverable strain of 94% in compression. The glass transition temperature of poly(vinyl alcohol) (PVA) in the aerogel was 49 K higher than that of pure PVA. The thermal stability of the GO/PVA aerogel in air environment was superior to that of dried GO in itself in thermogravimetric analysis (TGA).

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