Microstructural characterization of nanocellulose foams prepared in the presence of cationic surfactants
Marcos Mariano, Leandro Wang Hantao, Juliana da Silva Bernardes, Mathias Strauss
Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), Zip Code 13083-970, Campinas, São Paulo, Brazil.
Institute of Chemistry, University of Campinas (Unicamp), 13083-970 Campinas, Brazil.
In this work, we explore the architecture of highly porous foams based on cellulose nanofibers (CNFs) prepared by using cationic surfactants (e.g., C12TAB, C14TAB, and C16TAB) as modifying agents. The addition of surfactants to CNF suspensions led the nanoparticles surface to be covered by these molecules, reducing the zeta-potential from -35 to -8 mV, which, together with hydrophobic interactions of adsorbed surfactants, causes CNF flocculation. After freeze-casting and lyophilization, mechanical properties and pores structure of the low-density foams obtained (15.6 to 30.9 mg.cm-3) proved to be strongly dependent on nanofibers agglomeration degree. The primary causes of such dependence could not be observable by scanning electron microscopy but were found to be very significant on X-ray microtomography analysis. Total porosity, pore-size, and wall thickness of the foams were calculated and related to the surfactant chain size. Surface areas from 4.7 to 48.6 m2.g-1, obtained by n-decane adsorption, are reported.