Novel Micro- and Nano-particles Cellulose Based Pickering Emulsions.
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Novel Micro- and Nano-particles Cellulose Based Pickering Emulsions. Isabelle Capron, Hervé Bizot, Solène Grosbois, Heiko Winter, Bernard Cathala UR 1268 Biopolymères, Interactions, Assemblages – INRA – F44316 Nantes
ABSTRACT Emulsions are usually metastable systems of two non-miscible phases stabilized by surface active species like surfactant molecules. Emulsions stabilized by solid colloidal particles adsorbed at the interface (Pickering emulsions) offer some competitive advantages with respect to classical emulsions. Most studies published up to now concern emulsions stabilized by inorganic (metallic oxides, exfoliated clays, carbonates and phosphates) or polymeric particles while biomass derived alternatives have only been explored to a limited extent. For the first time, we report the stabilization of emulsions by unmodified cellulose nanocrystals [1, 2] . Cellulose nanocrystals were produced from bacterial cellulose and used to form Pickering emulsions. We demonstrate by SEM that the nanocrystals are adsorbed at the oil/water interface. We also study the size distribution of the droplets that was found to range around 4µm in diameter with very narrow dispersity. The stability of the emulsions was also investigated. The fabrication of new armored microparticles exposing cellulose acicular nanocrystals from cellulose nanocrystals opens opportunities to build materials from low cost and environmental friendly resource. INTRODUCTION An emulsion is a system of dispersed droplets of one immiscible liquid in another stabilized by emulsifiers. The Pickering emulsions present the particularity to be stabilised by solid particles [3, 4]. This type of emulsion is of particular interest because they are extremely stable against coalescence and a lower amount of particles is necessary for oil stabilisation compared to classical surfactants [4, 5] . They can then be used in a broad range of applications such as cosmetics, medical or food industries notably for emulsions as well as the fabrication of various functional materials. It is well known that cellulose can form micro- to nano- sized crystalline particles, the resulting size and morphology depending on both the cellulose origin (bacteria, alguae, plant or animal) and preparation conditions (time, temperature and acid type and concentration) [6 , 7] leading to average lengths varying from tens of nm to several µm. It has been established that hydrophobically modified cellulose can stabilise oil / water interface [8, 9]which implies series of chemical steps unfavourable on both environmental and financial point of view but none described oil in water emulsion stabilised by unmodified cellulose. We describe here Pickering emulsions stabilized by bacterial cellulose nanocrystals without further modification nor addition of any co-surfacting product.
EXPERIMENTAL Bacterial Cellulose Nanocrystals (BCN) were obtained from nata de coco according to previously reported procedures [10 , 11]. Briefly, nata de coco cubes were ground in a Waring Blendor at maximum speed. The
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