High dielectric composite film based on TEMPO-oxidized cellulose nanofibers/cationic modified BaTiO₃

High dielectric biobased composites of TEMPO-oxidized cellulose nanofibers (TOCNFs) reinforced with cationic modified barium titanate (BTO) nanoparticles were fabricated in this work. In order to greatly eliminate the agglomeration of the nanofiller and improve the dielectric properties of the resulting film, the modification of BTO was achieved via the cationization with an etherifying agent on the basis of cladding polydopamine around BTO. The results showed that the modified BTO nanofiller had a good interfacial compatibility and dispersion in the TOCNF matrix due to the ionic and hydrogen bonds formed between the cationic modified BTO and anionic TOCNFs. Meanwhile, the modified BTO reinforced composites exhibited better dielectric properties. Especially, the composite film with 40 wt% modified BTO exhibited an ultrahigh dielectric constant of 116.2 (at 1 kHz) and a breakdown strength of 57.7 kV/mm, which was 696% and 51.4% respectively higher than that of pure TOCNF film. It was noticed that the hydrophobicity of the composite films was also slightly improved without sacrificing its mechanical strength.