Exploiting electrostatic interactions between charged celluloses and carbon black to create conductive cryogels

Stable dispersions of cellulose and carbon nanomaterials (CNMs) are essential to design novel materials with enhanced electrical conductivity and mechanical strength. Several studies have shown colloidally stable dispersions of anionic celluloses and CNMs.¹ In contrast, cationic celluloses offer a promising but less-explored alternative for stabilizing CNMs in aqueous media.² This study investigates the interactions between carbon black (CB), a CNM, and charged celluloses (anionic or cationic) using X-ray photoelectron spectroscopy (XPS) and colloidal-atomic force microscopy (C-AFM). XPS analysis of cationic cellulose revealed a notable peak shift of 0.5 eV in the N 1s spectrum upon CB addition, indicating a strong interaction. Differently, for anionic cellulose, the addition of CB caused only a minor shift of 0.1 eV in the Na 1s spectrum. C-AFM showed that the cationic cellulose/CB system had an adhesion force of 2.2 ± 0.4 nN, 40% higher than the anionic cellulose/CB system (1.6 ± 0.5 nN). These findings indicate a stronger attractive interaction between CB and cationic cellulose. Both systems with cationic and anionic celluloses were then applied to prepare conductive cryogels. The favorable interactions between cationic fibrils and CB provided cryogels with a thin cellular framework, as revealed by X-ray microtomography. On the other hand, systems with anionic cellulose offered lower conductivity and a more irregular structure. Cationic cellulose/CB cryogels displayed low densities (<55 mg cm⁻³), high porosities (>91%), high specific modulus (11−21 MPa cm³ g⁻¹), tunable electrical resistivities (10¹−10⁸ Ω cm), and excellent fire resistance, highlighting a sustainable approach for producing conductive composites.

1. A. Hajian et al. Nano Letters 2017, 17 (3), 1439–1447.

2. A. Skogberg et al. Nanoscale 2022, 14, 448–463.