Chemical Modification of Semiconductor Surfaces by Means of Nanometric Cellulose Films

Cellulose films of nanometric thickness were produced by spin-coating on GaAs(100). Films were deposited using cellulose silylated solutions and subsequently regenerated by exposing them to vapors of hydrochloric acid. After regeneration, these films can strongly resist solvents. Modification of the film surface region was performed by immersing the regenerated cellulose films in a solution of phenyl isocyanate in dimethyl sulfoxide. A different functionalization was also successfully achieved through the interaction of the film surface with 4,4′-methylenebis(phenyl isocyanate) (MDI). Surfaces treated with MDI keep an unreacted isocyanate group and can again be modified by amines. For this purpose, 4-bromoaniline was used. All kinetics of the different molecular interactions with the cellulose film on GaAs were followed in situ using FTIRS in ATR/MIR (attenuated total reflection in multiple internal reflections) mode. Besides ATR/MIR having an analysis depth on the order of 1 µm, other surface techniques were used for analyzing these films with other probing depths such as X-ray photoelectron spectroscopy with ∼10 nm and high-resolution electron energy loss spectroscopy with ∼1 nm in the impact regime. The set of methods presented here represents a quite adequate way to study the surface chemistry of cellulose films and the procedures for their functionalization

Cellulose nanocrystal as ecofriendly stabilizer for emulsion polymerization and its application for waterborne adhesive

International audienceSoap-free emulsion polymerization of vinyl acetate (AVM) in the presence of cellulose nanocrystals (CNCs) was performed using persulfate/metabisulfite as initiator. The effect of the addition of MPEG comonomer on the locus of CNCs with respect to polymer particles was investigated. It was shown that the presence of MPEG strongly favors the accumulation of CNCs on the polymer particle thus contributing to a stabilization of polymer particle through Pickering effect. The rheological properties of the dispersion as well as the reinforcing effect of CNCs were also meaningfully affected by the presence of MPEG. For purpose of application, the polyvinyl acetate (PVA)/CNC nanocomposite dispersion was used as binder to produce PVA-based waterborne adhesive for wood. This open the way to produce high-value one pot nanocomposite dispersion ready for use, free from any surfactant likely to be used for waterborne adhesive or coating with higher mechanical performance

PREPARATION AND PROPERTIES OF STARCH-BASED BIOPOLYMERS MODIFIED WITH DIFUNCTIONAL ISOCYANATES

The present work reports on the preparation of thermoplastic starch (TPS) modified in situ with a diisocyanate derivative. Evidence of the condensation reaction between the hydroxyl groups of starch and glycerol with the isocyanate function (NCO) was confirmed by FTIR analysis. The evolution of the properties of the ensuing TPS, in term of mechanical properties, microstructure, and water sensitivity, was investigated using tensile mechanical, dynamic mechanical thermal analysis (DMTA), X-ray diffraction (XRD), and water uptake. The results showed that the addition of isocyanate did not affect the crystallinity of the TPS and slightly reduced the water uptake of the material. The evolution of the mechanical properties with ageing became less pronounced by the addition of the isocyanate as their amount exceeded 4 to 6wt%

Valorization of olive leaf waste as a new source of fractions containing cellulose nanomaterials

The olive oil activity generates annually a huge amount of biomass waste from the pruning action of the tree and fruit harvesting, including thin woody branches and leaves. In an effort toward more sustainability in the lignocellulosic biorefinery of olive waste activity, nanocelluloses (NCs) were produced from the solid residues remaining after the extraction of biological active compounds from the leaves. Fractions containing cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and lignin-containing cellulose nanofibrils (LCNFs) were prepared and characterized in terms of morphology, chemical composition, thermal stability, colloidal properties, and crystallinity. The reinforcing capability of the different fractions was evaluated in nanocomposite films made of an acrylic matrix incorporating different NC contents. Dynamic mechanical analysis (DMA) and tensile testing of the films were used to compare the reinforcing effect of the NCs. Although CNCs displayed the highest reinforcing effect based on the weight content, LCNFs and CNFs demonstrated also a reinforcing effect, which is higher when normalized with the cellulose content. Compared to CNFs and CNCs, LCNFs displayed a lower hydrophilic character confirmed by contact angle measurement, and had better thermal stability. This work demonstrated the potential use of the solid waste from olive leaves as a new source for biobased nanoparticles containing lignin, hemicellulose components, and cellulose nanofibrils. Beside the high content in bioactive polyphenol compounds that can be extracted from olive leaves, the conversion of the residual biomass can contribute to increasing the circularity and sustainability of olive oil activity

Enhancing mechanical and thermal properties of plasticized poly-L-(lactic acid) by incorporating aminated-cellulose nanocrystals

International audienceCellulose nanocrystals (CNCs) have attracted much interest as a nucleating and reinforcing agent for poly-L-(lactid acid) (PLLA). However, the processing route to incorporate CNCs into PLLA matrices and the CNCs content have a strong impact on the nucleating and reinforcing efficiency of the cellulose nanofillers (CNs). In the present work, a single melt-processing mode using poly(ethylene glycol) (PEG) as carrier for the CNCs and aminated CNCs (Am-CNCs), prepared via periodate oxidation followed by the addition of diaminododecane, was adopted to elaborate plasticized PLLA composites with different CN contents. The nucleating efficiency was investigated by differential scanning calorimetry using Avrami's approach to determine the half-crystallization time (t1/2). The influence of the CNCs content on the mechanical properties and melt rheology was also assessed by tensile test and frequency sweep measurements. The incorporation of CNCs and Am-CNCs resulted in a marked enhancement in both tensile modulus and strength, with an optimal effect at 2% nanofiller content, and the best performance for the Am-CNCs. A similar tendency was also observed for the melt rheology of the PLLA/PEG blend, which demonstrated a significant increase in both G and G with respect to the neat PLLA/PEG matrix. The results were justified by the effective nucleating ability of the CNCs and their dispersion degree within the plasticized PLLA matrix

Adsorption of cationic surfactant onto cellulosic fibers. I. Surface charge effects

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