Optimum Preparation Conditions for Highly Individualized Chitin Nanofibers Using Ultrasonic Generator

Preparation of zwitterionically charged chitin nanofibers through one step chemical modification and their application for antireflective coatings

Chitin nanofibers are widely used in many fields because of their biocompatibility, renewability and excellent mechanical properties. Herein, zwitterionically charged chitin nanofibers (ZC-ChNFs) were prepared from chitin via one step chemical modification (oxalic acid pretreatment) and subsequent ultrasound treatment. Effects of pretreatment time on size of the ZC-ChNFs and pH of ZC-ChNF suspensions on the thickness, porosity, refractive index and antireflective capacity of ZC-ChNF coatings were investigated. It was found that, by adjusting pH of the ZC-ChNF suspension, porosity and refractive index of the ZC-ChNF coatings could be controlled. The ZC-ChNF coatings fabricated with smaller ZC-ChNFs had higher antireflective performance and the transmittance gain of a glass with a ZC-ChNF coating was about 3.5 % at a wavelength of 550 nm compared to the bare glass. The results of this work provide a promising pathway to fabricate antireflective coating with ZC-ChNFs just by controlling the pH of ZC-ChNF suspensions.

Chitin nanofibers prepared by enzymatic hydrolysis: Characterization and application for Pickering emulsions

Chitin nanofibers (ChNFs) have a wide range of applications in numerous fields owing to their exceptional material properties and biological functionality. This research focused on producing ChNFs with diameters of 20-70 nm using chitinase and ultrasound from crayfish shells. The impact of enzymatic duration on ChNF yield and performance was investigated. Results revealed ChNFs forming a high aspect ratio network structure. Chitinase hydrolysis enhanced ChNF dispersion and yield while improving crystallinity and thermal stability without significantly altering their chemical structure. Enzymatically modified ChNF suspensions also exhibited stable rheological properties. Moreover, ChNFs showed good emulsification and emulsion stability in Pickering emulsion. The mechanism may be the effective adsorption of ChNFs at the oil-water interface, and the formation of a ChNF network in the continuous phase that prevents droplet coalescence. This study highlights that the potential of chitinase and ultrasound for the production of ChNFs and the utilization of crayfish shell waste.

Polyaniline-Grafted Chitin Nanocrystals as Conductive Reinforcing Nanofillers for Waterborne Polymer Dispersions

Due to its intrinsic electrical conductivity, polyaniline (PANI) is one of the most promising conducting polymers for high-performance applications in a wide range of technological fields. However, its poor dispersibility in water and organic solvents markedly imparts its processability and electrical conductivity. Herein, we report a green and one-step approach to preparing stable colloidal dispersions of highly dispersible hybrid nanoparticles by polymerizing PANI onto chitin nanocrystals (ChNCs) as biotemplates, via initiation through the surface amino groups of ChNCs. Evidence of the grafting of PANI onto ChNCs was supported by transmission electron microscopy (TEM), as well as Raman and Fourier transform infrared (FTIR) spectroscopies. Nanocomposite films were prepared by mixing the PANI-g-ChNCs with a waterborne poly(vinyl acetate) latex dispersion followed by casting and film formation at room temperature. The mechanical properties were tested as a function of the PANI-g-ChNC content. In addition, it was shown that at a proper content of PANI in ChNCs, and over a critical loading in the PANI-g-ChNCs, a conductive film was obtained, without sacrificing the reinforcing effect of the rodlike nanofiller. As a potential application, conductive waterborne adhesives for wood were prepared and the performance of the adhesives was tested. This research provides a facile route to fabricating a new class of hybrid nanofiller from a biobased origin, stable in water and easy to mix with waterborne dispersions, combining the merits of the ChNC nanofiller with the conductivity of PANI.

Optimization of Chitin Nanofiber Preparation by Ball Milling as Filler for Composite Resin

Chitin nanofiber is a nanomaterial produced by pulverizing chitin, the main component of crab shells. Since it has excellent mechanical properties, it is expected to be used as a reinforcing material to strengthen materials. Chitin was mechanically ground in water using a ball mill to prepare nanofibers. The ball size, total ball weight, and milling time were varied, and the resulting water dispersion and the cast film were analyzed to optimize the conditions for efficient preparation. The length and width of the nanofibers were also measured by SEM and AFM observations. The size of the balls affected the level of grinding and the intensity of impact energy on the chitin. The most efficient crushing was achieved when the diameter was 1 mm. The total ball weight directly affects the milling frequency, and milling proceeds as the total weight increases. However, if too many balls occupy the container, the grinding efficiency decreases. Therefore, a total ball weight of 300 g was optimal. Regarding the milling time, the chitin becomes finer depending on the increase of that time. However, after a specific time, the shape did not change much. Therefore, a milling time of approximately 150 min was appropriate.