Optical, morphological and photocatalytic properties of biobased tractable films of chitosan/donor-acceptor polymer blends

Effects of keto acid crosslinking on the structure and properties of chitosan based casted and hot-pressed films

Crosslinking is one of the most effective ways to enhance the performance of bio-based films, and suitable crosslinking agents are crucial for the enhancement. In this study, four α-ketoacids, namely glyoxylate, pyruvate, oxaloacetate, and α-ketoglutarate were used to crosslink chitosan at room temperature. The effects of crosslinking on the structure and properties of chitosan films were studied, and the reaction mechanism was explored. Fourier Transform Infrared spectroscopy and X-ray Photoelectron Spectroscopy indicated that ion attraction and Schiff base reactions occurred between keto acids and chitosan. Glyoxylate developed the most effective covalent crosslinking with chitosan, whereas α-ketoglutarate had the highest ionic crosslinking ratio. Keto acid crosslinking reduced the orderliness of chitosan, improved the uniformity of the film matrix and increased its UV-blocking capacity. Glyoxylate-crosslinked chitosan film demonstrated excellent tensile strength (160 MPa), water stability (water solubility about 11.71 %), and extremely low oxygen permeability (2.65 × 10-16 cm3·cm/cm-2·s-1· Pa-1). Despite the weakened thermal stability and water barrier property, glyoxylate crosslinking shows great potential for the preparation of high-strength and high‑oxygen-resistance chitosan films. Furthermore, the glyoxylate-crosslinked chitosan film could be produced by hot pressing and performed satisfactorily.

Effects of the Solvent Vapor Exposure on the Optical Properties and Photocatalytic Behavior of Cellulose Acetate/Perylene Free-Standing Films

The search to deliver added value to industrialized biobased materials, such as cellulose derivatives, is a relevant aspect in the scientific, technological and innovation fields at present. To address these aspects, films of cellulose acetate (CA) and a perylene derivative (Pr) were fabricated using a solution-casting method with two different compositions. Consequently, these samples were exposed to dimethylformamide (DMF) solvent vapors so that its influence on the optical, wettability, and topographical properties of the films could be examined. The results demonstrated that solvent vapor could induce the apparent total or partial preferential orientation/migration of Pr toward the polymer-air interface. In addition, photocatalytic activities of the non-exposed and DMF vapor-exposed films against the degradation of methylene blue (MB) in an aqueous medium using light-emitting diode visible light irradiation were comparatively investigated. Apparently, the observed improvement in the performance of these materials in the MB photodegradation process is closely linked to the treatment with solvent vapor. Results from this study have allowed us to propose the fabrication and use of the improved photoactivity "all-organic" materials for potential applications in dye photodegradation in aqueous media.

A facile approach for tuning optical and surface properties of novel biobased Alginate/POTE handleable films via solvent vapor exposure

Novel biobased films consisting of alginate blends with poly (octanoic acid 2-thiophen-3-yl-ethyl ester) (POTE), a conducting polymer, were prepared by solution casting, and their optical, morphological, thermal, and surface properties were studied. Using UV-visible spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), the effects of tetrahydrofuran solvent vapors on the optical properties and surface morphology of biobased films with different POTE contents were studied. Results indicate that morphological rearrangements of POTE take place during the process of solvent exposure. Specifically, the solvent vapor induced the formation of POTE small crystalline domains, which allows envisioning the potential of tuning UV-visible absorbance and wettability behavior of biobased films. Finally, theoretical electronic calculations (specifically frontier molecular orbitals analysis) provided consistent evidence on POTE's preferential orientation and selectivity toward the THF-vapor medium.

Two Fascinating Polysaccharides: Chitosan and Starch. Some Prominent Characterizations for Applying as Eco-Friendly Food Packaging and Pollutant Remover in Aqueous Medium. Progress in Recent Years: A Review

The call to use biodegradable, eco-friendly materials is urgent. The use of biopolymers as a replacement for the classic petroleum-based materials is increasing. Chitosan and starch have been widely studied with this purpose: to be part of this replacement. The importance of proper physical characterization of these biopolymers is essential for the intended application. This review focuses on characterizations of chitosan and starch, approximately from 2017 to date, in one of their most-used applications: food packaging for chitosan and as an adsorbent agent of pollutants in aqueous medium for starch.

Use of biocompatible redox-active polymers based on carbon nanotubes and modified organic matrices for development of a highly sensitive BOD biosensor

This work investigated the use of redox-active polymers based on bovine serum albumin and chitosan, covalently bound to mediators neutral red and ferrocene and containing carbon nanotubes, for immobilization of Paracoccus yeei VKM B-3302 bacteria. The structures of produced polymers were studied by IR spectroscopy and scanning electron microscopy. Cyclic voltammetry and impedance spectroscopy found the electrochemical characteristics of the investigated systems: the heterogeneous electron transfer rate constant, the constant of the rate of interaction with P. yeei bacteria and the impedance. The systems containing carbon nanotubes and ferrocene-based redox-active polymer proved to be the most promising. Biosensors formed using the hybrid polymers had a high sensitivity with the lower boundary of 0.1 mg/dm³ of the detected BOD₅ concentrations and a high correlation (R = 0.9916) with the standard BOD assay of surface water samples.