Polyvinyltrimethoxysilane-enhanced TEMPO-oxidized cellulose nanofiber aerogels for exceptional anisotropic thermal insulation, flame retardancy and oil/water separation

Nanocelluloses (NCs)-based aerogels with hierarchical microarchitecture are highly sought after for their extraordinarily thermal insulation and adsorption properties. Nevertheless, their intrinsic flammability, complex manufacturing processes, and inadequate mechanical characteristics substantially restrict their extensive practical applications. Herein, a Pickering emulsion templated sequential reaction strategy is employed to fabricate elastic NCs-based aerogels with hierarchically porous structures. The pivotal aspect of this synthesis resides in the Pickering emulsion phases, facilitating the in-situ construction of a polyvinyltrimethoxysilane (PVTMS) decorated framework. The resultant aerogels feature a low density and exhibit exceptional resilience. The material also displays exceptional anisotropic thermal insulating properties, with a peak value of 11.5 mW·m −1 ·K −1 along the axial direction and a value ten times greater, reaching 115.2 mW·m −1 ·K −1 , along the radial direction. Such a preparation method for the hybrid aerogels will offer noval perspectives in the field of advanced materials for multifunctional applications. • Preparation of PVTMS-enhanced TEMPO-oxidized cellulose nanofiber aerogels through two distinct drying methodologies. • The hybrid aerogels demonstrate superior flame retardancy enhancement. • The unidirectional aerogels exhibit better anisotropic thermal conductivity than the bidirectional aerogels. • Both unidirectional and bidirectional aerogels exhibit remarkable oil/water separation properties.