The association of nanoparticles with complementary properties to produce hybrids is an underestimated way to develop multifunctional original architectures. This strategy is used to prepare simple, low-cost, and environmentally friendly method to fabricate ultra-low density alveolar foam reinforced with carbon nanotubes (CNTs). This paper investigates the ability of cellulose nanocrystals (CNCs) to produce highly stable oil-in-water Pickering emulsions and to efficiently disperse carbon nanotubes in water to form three-dimensional macroporous conductive foam. It is shown that both single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) are strongly linked to CNCs by non-covalent interactions, preserving the intrinsic properties of both nanoparticles. Homogeneous surfactant-free emulsions with a droplet diameter of 6 µm are produced. Once concentrated, they can form stable high internal phase emulsions. Incorporating CNTs into these CNC-based emulsions was shown to improve their rheological properties. Freeze-drying the concentrated emulsions produces ultra-low density solid foams (14 mg·cm-3) with several levels of porosity controlled by the emulsification step. Loading CNCs with only 2-4 wt% of CNTs, decreases the electrical resistivity of the foam to 104 Ω cm in high relative humidity. The mechanical and electrical properties are studied and discussed in light of the resulting specific foam structure.
Keywords: Biobased; Cellular foam; Conductivity; Foam; Nanocellulose; Open cell structure; Pickering emulsion; Porous material.
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