A Sustainable approach for the Direct Functionalization of Cellulose Nanocrystals Dispersed in Water by Transesterification of Vinyl Acetate

Herein we report a novel method for a high-yield surface esterification of cellulose nanocrystals (CNCs) in water, by transesterification of vinyl esters. The esterified nanoparticles were simply produced by heating under stirring a water dispersion of CNCs in heterogeneous mixture with vinyl acetate, with potassium carbonate as catalyst. Reactions were performed in different conditions, to investigate the impact of different parameters, such as the amount of reagent, temperature and reaction time. In optimized conditions, the grafting level could be easily tailored by controlling the reaction time, and up to 90% of the accessible hydroxyl groups at the surface of the CNCs could be esterified. The acetylated CNCs retained their rod-like shape, while their dimensions, crystallinity and thermal stability were marginally affected by the treatment. Turbiscan analysis finally revealed that the hydrophobic character at the surface of the modified particles increased with the acetylation level, leading to a commensurate modification of their dispersive properties in water, acetone and THF

Dispersibility and Emulsion-Stabilizing Effect of Cellulose Nanowhiskers Esterified by Vinyl Acetate and Vinyl Cinnamate

The surface of cotton cellulose nanowhiskers (CNW's) was esterified by vinyl acetate (VAc) and vinyl cinnamate (VCin), in the presence of potassium carbonate as catalyst. Reactions were performed under microwave activation and monitored by Fourier transform infrared (FT-IR) spectroscopy. The supramolecular structure of CNW's before and after modification was characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Distinctively from the acetylation treatment, an increase in particles dimensions was noted after esterification with VCin, which was assigned to pi-pi stacking interactions that may exist between cinnamoyl moieties. The dispersibility and emulsion stabilizing effect of acylated CNW's was examined in ethyl acetate, toluene, and cyclohexane, three organic solvents of medium to low polarity. The acylated nanoparticles could never be dispersed in toluene nor cyclohexane, but they formed stable dispersions in ethyl acetate while remaining dispersible in water. Stable ethyl acetate-in-water, toluene-in-water, and cyclohexane-in-water emulsions were successfully prepared with CNW's grafted with acetyl moieties, whereas the VCin-treated particles could stabilize only the cyclohexane-in-water emulsions. The impact of esterification treatment on emulsion stability and droplets size was particularly discussed

Cellulose nanocrystals and microfibrillated cellulose as building blocks for the design of hierarchical functional materials

In this article, we highlight the potential of nanocelluloses, such as cellulose nanocrystals (CNC) and microfibrillated cellulose (MFC), to serve as building blocks for the design of hierarchical functional nanomaterials. Four categories of value-added nanomaterials are envisaged here, namely aerogels, emulsions, templated materials and stimuli-responsive nanodevices. But most importantly, we demonstrate that appropriate functionalization methods are required in order to tailor the nanocellulose surface and further design materials with required characteristics

A comparative study on the acetylation of wood by reaction with vinyl acetate and acetic anhydride

A comparative study on the acetylanon of maritime pine wood by reaction with vinyl acetate (VA) and acetic anhydride (AA) has been undertaken The reactivity of wood cellulose and lignin with regards to VA or AA was examined using different techniques The products dissolved in the reaction medium after acetylation of wood by the two different methods were analyzed by HPLC chromatography Results suggested that the cellulose sites in wood were more attacked by VA than by AA in our experimental conditions Besides the unreacted cellulose sites of the AA-acetylated sample could be further esterified by vinyl propionate which (13)C NMR signals could be differentiated from the acetyl signals The esterified materials obtained after modification of isolated cellulose and lignin were also characterized by FTIR (13)C CP-MAS NMR and (13)P NMR spectroscopy and compared Results indicated that VA could acetylate both biopolymers but they also showed that AA reacted more readily with lignin than VA Moreover FTIR spectroscopy revealed that unexpected side reactions concurrently occurred in lignin when VA was used It is hypothesized that some C-acetylation also took place between VA and a number of lignin aromatic rings during the treatment

Carbohydrate Polymers

In this paper, we propose both a new application for cellulose micro-beads and a new concept in colloidal lithography to directly deposit and template a metal from ions transported by the organized colloidal particles, using the colloidal particles themselves. To do so, 5 μm-sized cellulose micro-beads (CμBs) were first surface-functionalized by trimellitic anhydride to introduce carboxylate ligands before decorating them with Cu2+ ions by complexation of the carboxylate groups with a CuCl2 solution. The Cu2+-loaded CμBs, dispersed in an aqueous phase, were organized in compact monolayer at the vicinity of a planar electrode. The release of cupric ions and subsequent copper deposition were triggered by an electric field delivered by a tension generator. 2D non-close-packing arrays of copper dots assemblies displaying hexagonal symmetry were generated below or around the micro-beads – depending on the ions concentration in the aqueous phase – leading respectively to copper dots deposited circularly or concentrated in rings. The Cu2+-loaded cellulose beads allowed the covering of 2 cm²-surfaces by copper patterns in less than 45 min, using an easy and cheap process

Synthesis of surfactant-free micro- and nanolatexes from Pickering emulsions stabilized by acetylated cellulose nanocrystals

Surfactant-free micro- and nanolatexes from Pickering emulsions stabilized by acetylated cellulose nanocrystals (CNCs).</p