Controlling Miscibility of the Interphase in Polymer-Grafted Nanocellulose/Cellulose Triacetate Nanocomposites

The miscibility at the interphase of polymer-grafted nanocellulose/cellulose triacetate (CTA) composite films was tailored using different casting solvents. The polymer-grafted cellulose nanofibrils were prepared by modifying surfaces of 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized nanocellulose with amine-terminated poly(ethylene glycol) (PEG). The PEG-grafted nanocelluloses were individually dispersed in dichloromethane, 1,4-dioxane, and N,N-dimethylacetamide. The PEG-grafted nanocellulose/CTA composite films were prepared by mixing the nanocellulose dispersion and CTA solution and subsequent casting-drying. The miscibility of PEG and CTA at the interphase of the composite was controlled by controlling the solvent, which was confirmed by dynamic mechanical analysis. All the composite films showed high optical transparency. However, the mechanical properties of the composites differed because of the difference in the PEG/CTA interfacial miscibility. The composite films with better PEG/CTA interfacial miscibility showed higher Young's modulus, strength, and toughness. This interfacial design technique paves the way to exploiting the reinforcing potential of highly transparent and hydrophobic surface-grafted nanocellulose/polymer composite materials.

Effects of fabrication parameters on viscoelastic shear modulus of 2,3-dialdehydecellulose membranes--potential scaffolds for vocal fold lamina propria tissue engineering

Porous 2,3-dialdehydecellulose (2,3-DAC) membranes were investigated for use as a synthetic scaffold for engineering vocal fold-like tissues. Two criteria of this application are (i) the viscoelastic shear properties of the scaffold should be controllable in the range of vocal fold tissues and (ii) scaffolds should remain biomechanically stable to withstand vibrational stresses in a bioreactor. Porous 2,3-DAC membranes were fabricated from methylolcellulose by water-induced cellulose regeneration, with or without sodium chloride leaching, followed by periodate oxidation. They were freeze-dried and ethylene oxide-sterilized. Different degrees of oxidation were obtained on reacting with sodium metaperiodate for different time points. Rheological studies were performed to investigate the effect of freeze-drying, porosity, degree of oxidation, sterilization, and incubation time on elastic and viscous shear moduli, G' and G'', respectively, for frequencies 0.01-10 Hz. Freeze drying increased G' and G'', while increased porosity and degree of oxidation reduced G' and G''. Sterilization had no effect on viscoelasticity. When incubated in Dulbecco's minimum essential medium at 37 degrees C, membranes with 6-7% and 19-20% oxidation disintegrated after 7 and 3 days, respectively, while membranes with 3-4% oxidation showed little viscoelastic change over a period of 42 days. The upper frequency limit of rheologic measurement was a limitation of the study and should be addressed in future investigations.

A statistical design to evaluate the influence of manufacturing factors on the material properties and functionalities of microcrystalline cellulose

The aim of this study is to statistically evaluate the effects of manufacturing factors on the material properties and functionalities of microcrystalline cellulose (MCC) products. How the material properties of MCC products dominate their functionalities was further explored. Results demonstrate that the desired material properties and functionalities of MCC products can be obtained by manipulation of the manufacturing factors using proper polynomial equations, and the key manufacturing factor is temperature. On the other hand, the functionalities can be quantitatively predicted by material properties. Meanwhile, the key material property is molecular mass in controlling MCC functionalities. The particle morphologies may also serve as important material properties. In conclusion, the careful control of temperature during the manufacture of MCC might minimize inter-batch variation. The correlation of the material properties of MCC products with their functionalities might help the formulation designer rationally select proper MCC products. The universal harmonization of MCC products might be achieved by the regulation of their molecular mass, surface roughness, and roundness.