The viscosity curves of pure CNF emulsions present the obvious sharp decrease at about 10 s −1, however, the mixture of CNF and crystallized CNC did not show that anymore, which proved the crosslinked feature in the aqueous phase affected CNF flexible matrixes rather than the dense aggregation of rod-like CNC particles. studied different CNC particles fabricated from pure CNF by hydrolyzation with sulfuric acid-for 1, 2, and 4 h. On the contrary, CNF dispersions with larger aspect ratios exhibited solid-like viscoelastic behavior and larger concentrations result in increasing viscosity and its plateau at low shear rates, which associate from the specific entangled network. reported that CNC dispersion, containing needle-like crystals of smaller aspect ratio, exhibited elastic gel-like rheological properties, but at lower CNC concentration, a concentration dependence on viscosity was found, i.e., a liquid-like behavior. For dispersion formation by CNC and CNF, Du et al. In appearance, different aspect ratio celluloses impact the rheology and morphology of corresponding dispersion and emulsion. CNC and CNF possess abundant hydroxyl groups that allow potential hydrogen bonds and surface modification, which the surface chemistry associates with pre-treatment and refinement approaches from specific cellulose sources. 90%), while CNF with micrometer-long entanglements contains both amorphous and crystalline domains. As spindle-like or rod-like particles, CNCs possess near-perfect crystallinity (ca. In general, emulsions stabilized with CNF or CNC can behave in a gel-like manner because of strong and irreversible cellulose adsorption to the O/W (oil/water) interface, based on steric interfacial stabilization. Cellulose nanocrystal (CNC), microfibrillated cellulose (MFC), bacterial nanocellulose (BNC), and cellulose nanofibers (CNF) belong to the class of nanocellulose. It is an amphiphilic organic polymer, with a diameter between 1~100 nm. Nanocellulose refers to ultra-fine cellulose. These glucose (hexose) units comprise abundant hydroxy and carboxyl moieties as hydrophilic groups and a polymer backbone and are widely applied as biocompatible emulsifiers and thickeners. Cellulose, the natural, environmental, and renewable material, consists of dehydrated glucose units. Besides those, also immiscible polymer blends are important emulsions, when both components are in the molten state. This paper provides information on how a systematical variation of the composition influences morphology and physico-chemical interactions as detected by broadband dielectric spectroscopy and rheological behavior.Īn emulsion is a dispersed system composed of two immiscible liquid phases, usually an oil and an aqueous phase with an emulsifier (surfactant or Pickering emulsifier) adsorbed at the interface. To evaluate the results further, they were compared with CNF dispersions (without oil phase), which showed a surfactant effect slightly on maximum stress but strongly on yield stress τ y, indicating that DDAB can promote the formation of a CNF network rather than the viscosity of the whole system. Similarly, a higher CNF content leads to a higher viscosity and yield point, but at high DDAB contents, the viscosity function exhibits an S-shape at intermediate CNF contents. Increasing the DDAB content promotes the solubilization of CNF in the aqueous phase, which will increase the overall viscosity and yield points. The dielectric damping exhibits a minimum, whose value decreases with increasing DDAB and CNF content. Polarized optical microscopic images reveal that the droplets tend to shrink at higher CNF content but grow bigger when increasing the DDAB content, which is proved by fluorescence analysis of the CNF dispersibility with varying DDAB content. The CNF and DDAB contents were systematically varied while the water-to-paraffin oil ratio was kept constant to discern the influence of the Pickering emulsifiers. Cellulose nanofiber (CNF)-based Pickering emulsions are good systems to research these properties with respect to their microscopic phase structure, dielectric, and rheological properties by using CNF as a water-dispersible Pickering emulsifier, liquid paraffin as an oil phase, and didodecyldimethylammonium bromide (DDAB) as a cationic auxiliary surfactant. The dispersibility of flexible polymer chains present at the emulsion’s interface between the dispersed and continuous phase has obvious effects on rheology and dielectric properties of the whole emulsion.
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