pH-responsive cellulose–chitosan nanocomposite films with slow release of chitosan

Abstract

Cellulose-chitosan films were prepared using a physical method in which cellulose and chitosan were separately dissolved via freeze thawing in LiOH/urea and mixed in different proportions, the resulting films being cast and regenerated in water/ ethanol. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) spectroscopy verified the composition changes in the nanocomposites due to different mixing ratios between the polymers. Tensile stress-strain measurements indicated that the mechanical performance of the cellulose-chitosan nanocomposites slightly worsened with increasing chitosan content compared with that of films comprising cellulose alone. Field emission scanning electron microscopy revealed the spontaneous formation of nanofibers in the films; these nanofibers were subsequently ordered into lamellar structures. Water uptake and microscopy analysis of film thickness changes indicated that the swelling dramatically increased at lower pH and with increasing chitosan content, this being ascribed to the Gibbs-Donnan effect. Slow material loss appeared at acidic pH, as indicated by a loss of weight, and quantitative FT-IR analysis confirmed that chitosan was the main component released. A sample containing 75% chitosan reached a maximum swelling ratio and weight loss of 1500% and 55 wt%, respectively, after 12 h at pH 3. The study presents a novel way of preparing pH-responsive cellulose-chitosan nanocomposites with slow-release characteristics using an environmentally friendly procedure and without any chemical reactions.

Morphology, mechanical, and physical properties of wet‐spun cellulose acetate fiber in different solvent‐coagulant systems and in‐situ crosslinked environment

“…However, large increase in swelling is observed in basic medium. Degree of swelling depends on the ionization of carboxyl groups 64 . In the presence of hydrochloric acid, water can convert the ester bonds present in CA into carboxylic acid groups.…”

Cellulose‐Based Fully Green Triboelectric Nanogenerators with Output Power Density of 300 W m−2

“…The cellulose was dissolved according to the reported method. [ 36,37 ] R‐cellulose films were prepared by casting the solution onto glass plates (with a thickness corresponding to the desired thickness in the dry state) and immersed into an ethanol regeneration bath for 2 h. The films were placed in a Milli‐Q water bath to wash away the LiOH and urea, and the water was changed daily until pH 7 was reached. The films were dried at room temperature for ≈8 h; to avoid shrinkage, each film was placed on a plastic plate, and all film edges were taped.…”

“…The R‐cellulose was produced in our laboratory using an environmentally friendly method. [ 36–38 ] A 20 µm thick flexible and transparent film ( Figure a) with a density of 1.4 g cm −3 was made from dissolved cellulose. The surface of the film was characterized by scanning electron microscopy (SEM) in secondary electron (SE) mode (Figure 1a).…”

“…[ 42 ] Thereby the CNF films will adsorb moisture/water more strongly than underivatized cellulose. [ 36,43,44 ] The binding of water significantly reduces the triboelectric effect, [ 45 ] which suggests why the measured triboelectric effects of fibrillated cellulose and paper in most studies are relatively weak. In our experiment, cellulose films were formed from dissolved cellulose polymers that are molecules, not fibers, resulting in films with densities of 1.4 g cm −3 , which is close to the nominal value of pure cellulose: 1.5 g cm −3 .…”

Chitosan‐based biomaterials: From discovery to food application

“…This method can be used to increase the scale of chitosan production. In addition, some natural or synthetic materials with low eutectic solvents have been used to improve the preparation scale of chitosan derivatives 58‐60 …”