Pickering Emulsions and Hydrophobized Films of Amphiphilic Cellulose Nanofibers Synthesized in Deep Eutectic Solvent

Abstract

Herein, a dual-functioning deep eutectic solvent system based on triethylmethylammonium chloride and imidazole was harnessed as a swelling agent and a reaction medium for the esterification of cellulose with n-octyl succinic anhydride (OSA). The modified or amphiphilic cellulose nanofibers (ACNFs), synthesized using three different OSA-to-anhydroglucose unit molar ratios (0.5:1, ACNF-1; 1:1, ACNF-2; and 1.5:1, ACNF-3), were further converted into nanofibers with degree of substitution (DS) values of 0.24−0.66. The ACNFs possessed a lateral dimension of 4.24−9.22 nm and displayed surface activity due to the balance of hydrophobic and hydrophilic characteristics. The ACNFs made stable aqueous dispersions; however, the instability index of ACNF-3 (0.51) was higher than those of ACNF-1 (0.29) and ACNF-2 (0.33), which was attributed to the high DS-induced hydrophobicity, causing the instability in water. The amphiphilic nature of ACNFs promoted their performance as stabilizers in oil-in-water Pickering emulsions with average droplet sizes of 4.85 μm (ACNF-1) and 5.48 μm (ACNF-2). Self-standing films of ACNFs showed high contact angles for all the tested DS variants (97.48− 114.12°), while their tensile strength was inversely related to DS values (ACNF-1: 115 MPa and ACNF-3: 49.5 MPa). Aqueous dispersions of ACNFs were also tested for coating fruits to increase their shelf life. Coatings improved their shelf life by decreasing oxygen contact and moisture loss.

Silicone Oil/Water Pickering Emulsions with Surface-Hydrophobized Cellulose Nanofibers Formed via In Situ Homogenization with Amino-Silicone

“…The Sample II film exhibited a higher light transparency and a lower haze value than those of the Sample V film (Figure a). The transparent film prepared from the Sample II emulsion is characteristic, differing from those prepared from o/w emulsions prepared with chemically modified CNFs . This is probably because the Sample II film had a small pore volume and small pore volume distribution owing to the close packing structures of the silicone oil/TEMPO–CNF/amino-silicone particles with their small and homogeneous sizes (Figure S11).…”

Multifunctional Biogenic Films and Coatings from Synergistic Aqueous Dispersion of Wood-Derived Suberin and Cellulose Nanofibers

“…Amphiphilic CNF was obtained through the consecutive esterification of kraft pulp with OSA in a DES based on imidazole and TEMACl, followed by the mechanical disintegration of the amphiphilic pulp using a microfluidizer (Qasim et al, 2023). The DES reaction medium was formed by compounding imidazole and TEMACl at a molar ratio of 7:3.…”

“…Li et al, 2020). In our previous study, we developed amphiphilic CNF using a dual-functioning deep eutectic solvent (DES) to create highly stable oil-in-water Pickering emulsions (Qasim et al, 2023). We hypothesize that these amphiphilic CNF could possess a strong affinity for hydrophobic suberin to form a uniform dispersion of suberin in water.…”