Fibril surface chemistry

Fourier-transform infrared spectroscopy (FT-IR) is the most commonly used technique for evaluation of the chemistry of surface-modified cellulose microfibrils and nanocrystals (whiskers) [25,51,52,57-60]. However, FT-IRanalysis is not confined to the surface of the material, and is therefore best suited for qualitative evaluations of the chemistry of microfibrillar cellulose. 

NMR has also been used to obtain information about the chemical composition of microfibril surfaces [39, 50, 58, 61]. As with FT-IR, the method is sensitive to the bulk properties of the sample, and the low signal-to-noise ratio make identification of the chemical structure of the surface difficult. 

Probably the most suitable technique for evaluation of cellulose microfibril surface chemistry is X-ray photoelectron spectroscopy (XPS) [62]. The method provides a full elemental analysis, except for hydrogen, of the topmost 1-20 nm of the sample surface. High-resolution XPS Cls measurements give quantitative information on carbon bonding chemistry [63], XPS has been used extensively to quantify the changes of the chemical composition in the microfibril surface during derivatiza-tion [25-27, 60, 64]. 

Bulk sensitive elemental analysis [19, 38, 39, 52, 53, 60], zeta-potential measurements [27] and various titration techniques [34, 39, 40, 50, 58, 59] have also been employed for chemical characterization of fibril surfaces. 

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The transient current signals generated during sliding contact between a stainless steel stylus and a polymer substrate are strongly affected by the micromechanics of the sliding interface (fibril formation, fracture) and the surface chemistry along the interface. These currents are especially sensitive to surface... 

Many layered biological systems resemble cholesteric liquid crystals in the rotation of orientation from layer to layer. This has raised recent interest in whether they actually are liquid crystals, in that the rotation forms spontaneously as a result of interactions between fibers in successive layers. This would occur in a fluid state, which is subsequently embedded in a hard matrix. The core question is really whether the rotation pattern is directly controlled by some form of oriented extrusion during the deposition process or is controlled through the surface chemistry of fibrils deposited in successive layers. 

The positioning of fibrils between the lithographic columns was made specific through the use of both noncovalent and covalent chemistry shown in Figure 16. Dinca first deposited a layer of photobiotin on the column surface, this layer was then exposed to ultraviolet light in order to activate... 

Because the yellow fibrils comprising the body-only image are confined to the uppermost portions of the threads of the cloth, mechanisms that would evidence migration by capillary action can be excluded. Our attempts to reproduce this surface quality of the image have been most successful with various catalyzed-decomposition contact mechanisms. Laboratory simulations (8) have produced very convincing results both in chemistry and appearance see Figure 8). 

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