Green Topochemical Esterification Effects on the Supramolecular Structure of Chitin Nanocrystals: Implications for Highly Stable Pickering Emulsions

Abstract

In nature, chitin is organized in hierarchical structures composed of nanoscale building blocks that show outstanding mechanical and optical properties attractive for nanomaterial design. For applications that benefit from a maximized interface such as nanocomposites and Pickering emulsions, individualized chitin nanocrystals (ChNCs) are of interest. However, when extracted in water suspension, their individualization is affected by ChNC self-assembly, requiring a large amount of water (above 90%) for ChNC transport and stock, which limits their widespread use. To master their individualization upon drying and after regeneration, we herein report a waterborne topochemical one-pot acid hydrolysis/Fischer esterification to extract ChNCs from chitin and simultaneously decorate their surface with lactate or butyrate moieties. Controlled reaction conditions were designed to obtain nanocrystals of a comparable aspect ratio of about 30 and a degree of modification of about 30% of the ChNC surface, under the rationale to assess the only effect of the topochemistry on ChNC supramolecular organization. The rheological analysis coupled with polarized light imaging shows how the nematic structuring is hindered by both surface ester moieties. The increased viscosity and elasticity of the modified ChNC colloids indicate a gel-like phase, where typical ChNC clusters of liquid crystalline phases are disrupted. Pickering emulsions have been prepared from lyophilized nanocrystals as a proof of concept. Our results demonstrate that only the emulsions stabilized by the modified ChNCs have excellent stability over time, highlighting that their individualization can be regenerated from the dry state.

Environmental Sustainability and Physicochemical Property Screening of Chitin and Chitin-Glucan from 22 Fungal Species

“…As such, the smaller L 020 is observed for the AAj species (2.3 nm, solely α-chitin), while a L 020 of 5.4 nm is detected for GF , PC , PE , and PF species (α-chitin and glucans). It is important to note that these L 020 values are significantly lower than 8–9 nm observed for chitin nanocrystals from crustacean shells . This smaller crystalline size is consistent with the reduced crystallinity degree observed and is a characteristic of poorly crystalline biopolymers …”

“…As summarized in Table S3, estimated crystallinity degrees vary greatly, ranging from 28 to 78%. In all cases, the crystallinity degree remains below the 76% reported for the pure shrimp shell chitin, 41 the 85% for chitin nanocrystals isolated by HCl hydrolysis, 50 or the 92% achieved for chitin nanocrystal isolated from waste shrimp shells by TEMPO-oxidation. 51 This suggests that the isolation process used to extract the chitin (using a weak acid and short reaction times) preserves the low molecular amorphous chitin.…”

“…It is important to note that these L 020 values are significantly lower than 8−9 nm observed for chitin nanocrystals from crustacean shells. 50 This smaller crystalline size is consistent with the reduced crystallinity degree observed and is a characteristic of poorly crystalline biopolymers. 57 Fourier transform infrared spectroscopy (FTIR) is a suitable method for studying conformation and packing mode of chitin macromolecules.…”

Chitosan–poly(vinyl alcohol)–ionic liquid-grafted hydrogel for treating wastewater

“…The crystal size was calculated using the Scherrer equation (eqn (5)). 35 where Dp is the average crystal size, β is the line-broadening in radians (full width at half-maximum (FWHM)), k is the Scherrer constant (0.9), λ is the X-ray wavelength, and θ is the Bragg angle. The crystalline sizes of CS, PVA, CS–PVA mixture, CS–PVA–IL gel, and CS–PVA–IL gel after dye adsorption ( CS–PVA–IL gel–dye) were 3.91, 2.77, 1.86, 3.15, and 4.93 nm, respectively (Fig.…”

Amphiphilic Mesoporous Foam-Stabilized Pickering Emulsions as Versatile Nanoreactors for In Vitro Drug Metabolism

“…Mesoporous graphene-based materials with variable surface properties have been widely applied in the fields of environment, energy, catalysis, and so forth. , The mesoporous structure not only prevents graphene sheets from restacking but also provides graphene materials with a high specific surface area, an interconnected conductive network, and a specific microenvironment due to the combination of a porous structure with the excellent intrinsic properties of graphene. , It is interesting to note that mesoporous graphene foam (GF) induced by phytic acid (PA) possesses unique super-amphiphilicity expect for the inherent excellent properties . Therefore, the super-amphiphilic GF was used as an emulsifier to stabilize the Pickering emulsion for CYP450s-catalyzed metabolism.…”