Chemical Structure Of Chitosan Research Articles

Degradation of β-chitosan by solution plasma process (SPP)

In this work, the solution plasma process (SPP) is used to treat β-chitosan solutions in order to induce the degradation of chitosan. The effects of solution plasma on the properties of chitosan solutions are investigated. The treatment time was varied from 0 to 300 min. The plasma-treated chitosan was characterized by the following methods; molecular weight by GPC, viscosity, crystal structure by XRD, chemical characteristics by FT-IR, solubility by UV–vis spectrophotometer, and fractional analysis. The results showed that after treatment with plasma for 15–120 min, the viscosity of the chitosan solution and apparent molecular weight of chitosans decreased remarkably, when compared to those of untreated sample. Longer treatment times had less effect on both viscosity and molecular weight of the samples. This suggested that the degradation process of chitosan occurred during plasma treatment. The XRD analysis showed that the crystallinity of chitosan was destroyed, resulting in amorphous structure. FT-IR analysis revealed that chemical structure of chitosan was not affected by solution plasma treatment. The %yield of water-soluble chitosan was increased with increasing plasma treatment time. These results implied that solution plasma process is able to induce the degradation of chitosan solutions.

The Influence of the Chemical Structures of Chitosan and Acid Dye on the Adsorption Process

The objective of this paper is the study of the influence of the chemical structures of adsorbent and adsorbate on the adsorption process. By using of crab shell chitosan (CC) and deep‐pink shrimp chitosan (CP) for removal of acid 183 and AR114 from aqueous solutions, it is shown that CP, which corresponds to the highest molecular weight, is the most efficient adsorbent material. In addition, the best extent of decolorization is obtained for AR 183 that is the smallest molecule. Langmuir model represents the best fit of the experimental data, indicating monolayer coverage of chitosan outer surface. Pseudo‐second order kinetic model describes accurately the adsorption processes, suggesting chemical rate limiting steps. The positive values of the enthalpy changes indicated endothermic attachment of dyes to the biomaterials. CP/AR183 system corresponds to the most energetically favorable phenomenon. Besides, desorption of AR from chitosan was found to be very low in acidic aqueous medium for all couples.

Preparation of low molecular weight chitosan using solution plasma system

Abstract The solution plasma system was introduced to treat chitosan solution in order to prepare low molecular weight chitosan. The plasma treatment time was varied from 0 min to 300 min. The plasma-treated chitosan was characterized including viscosity, molecular weight by GPC, and chemical characteristics by FT-IR. The results showed that after treated with plasma for 15–60 min, the viscosity of chitosan solution and apparent molecular weight of chitosans were remarkably decreased, compared to those of untreated sample. Longer treatment time had less effect on both viscosity and molecular weight of samples. Eventually, long treatment time (≥180 min) showed no influence on both viscosity and apparent molecular weight. This suggested that the degradation process of chitosan occurred during plasma treatment. FT-IR analysis revealed that chemical structure of chitosan was not affected by solution plasma treatment. TOF-MS results showed that chitooligosaccharides with the degree of polymerization of 2–8 were also generated by solution plasma treatment. The results suggested that solution plasma system could be a potential method for the preparation of low molecular weight chitosan and chitooligosaccharides.

Physicochemical and structural characteristics of chitosan nanopowders prepared by ultrafine milling

Two different molecular weights of chitosan were pulverized to nanopowders by ultrafine milling. The nanopowders were characterized by viscometry small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), FT-IR spectroscopy and UV-vis spectroscopy. Our results showed that ultrafine milling effectively reduced the particle size of chitosan to a nanoscale. The viscosity average molecular weight (Mv) of chitosan was decreased by the milling treatment. The crystalline structure of chitosan was destroyed by the milling since the nanopowder exhibited an amorphous XRD pattern. In addition, thermal stability of the low molecular weight chitosan was decreased after the milling treatment. FT-IR and UV-vis spectra showed that the milling process did not cause significant changes in the chemical structure of chitosan.

Cross-linked succinyl chitosan as an adsorbent for the removal of Methylene Blue from aqueous solution

Removal of a basic dye (Methylene Blue) from aqueous solution was investigated using a cross-linked succinyl-chitosan (SCCS) as sorbent. The chemical structures of chitosan and its derivatives were testified by FT-IR. X-ray diffraction, DTG analysis and swelling measurements were conducted to clarify the characteristics of the chemically modified chitosan. The effect of process parameters, such as pH of the initial solution, and concentrations of dyes on the extent of Methylene Blue (MB) adsorption was investigated. The Langmuir isotherm model was used to fit the equilibrium experimental data, giving a maximum sorption capacity of 289.02mg/g at 298K. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were determined to be −25.32kJmol−1, −6.76kJmol−1 and −62.36Jmol−1K−1, respectively, which leads to a conclusion that the adsorption process is spontaneous and exothermic.

Miscibility and interactions in chitosan acetate/poly(N-vinylpyrrolidone) blends

In the present study, the blends of chitosan (Ch) and poly(N-vinylpyrrolidone) (PVP) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). WAXD patterns of homopolymers and their blends indicated that blending of amorphous materials, such as PVP, with semicrystalline polymer, such as chitosan gives rise to an amorphous structure. From thermal curves the glass transitions temperature have been determined and compared. The thermal results indicated that in the solid ChA/PVP blends the components are poorly miscible. The FTIR spectra of film blends, in the carbonyl stretching region of PVP and the hydroxyl stretching bands of chitosan have been analyzed. The observed shift of these bands and the change of their shape depends on (I) the blend composition, on (II) the chemical structure of chitosan {chitosan in its amine form (Ch) or chitosan acetate (ChA)}, and on (III) the molecular weight of PVP, whereas the influence of temperature in the range of 298–403 K seems to be negligible.

Treatment of real effluents from dyeing reactor: Experimental and modeling approach by adsorption onto chitosan

This work aims to study the treatment (decolorization) of real industrial dyeing effluents originated directly from the dyeing bath, before entering the equalization tank (instead of treating the whole volume of wastewater) using chitosan beads as adsorbents. The addition of amido and imino groups on chitosan backbone through grafting reactions increased the adsorption capacity of adsorbents, while the cross-linking method made them capable of reuse for ten cycles at least without significant loss of their capacity (∼5%). The imino grafted derivative with a dosage of 5 g/L resulted in a residual dye content <1 mg/L, which is in accordance with the limitations of legislation. Swelling experiments demonstrated low swelling percentages (∼35%) for the prepared adsorbents. Equilibrium data were successfully fitted to the Langmuir–Freundlich model (L–F). Kinetic data were fitted to a proposed detailed mathematical model, based on the chemical structure of chitosan and on a valid single-component adsorbate approximation, resulting in diffusion coefficients of dyes in the triple dye mixture (both in simulated/synthetic and real effluents). A commercial form of activated carbon was used, to compare and confirm the high adsorption capacity and easy/successful regeneration of the prepared chitosan derivatives (through adsorption–desorption experiments in real effluent).

Electrospun Chitosan Nanofibers for Hepatocyte Culture

In this study, we developed a method to obtain high surface area nanofiber meshes composed of chitosan of a number of molecular weights. This method required decreasing the viscosity and surface tension of the chitosan solution as well as optimization of the electrospinning parameters such as applied voltage and environmental humidity. These chitosan nanofiber meshes were developed as a culture substrate for hepatocytes. The fibers exhibited a uniform diameter distribution (average diameter: 112 nm) and FTIR results indicate that the chemical structure of chitosan is stable during the electrospinning process. The attachment, morphology and activity of hepatocytes cultured on the chitosan nanofiber meshes were tested. The results showed that the chitosan nanofibers are biocompatible with hepatocytes and that these chitosan nanofiber meshes could be useful tissue culture substrates for various applications, including bioartificial liver-assist devices and tissue engineering for liver regeneration.

Preparation and Properties of Amphiphilic Chitosan Derivative as a Coagulation Agent

A novel chitosan-based polymeric surfactant, Oleoyl-Carboxymethyl chitosan (O-CMCS) was produced as a coagulation agent to clean the residual oil from the wastewater of oil extraction (WWOE). O-CMCS was synthesized by reacting carboxymethyl chitosan (CMCS) with oleoyl chloride. The chemical structures of chitosan and its derivatives were characterized by FTIR. The destabilization of oil in water was successfully actualized by the application of O-CMCS (the optimal adsorbent with a dosage of 0.2 g/L; mixing time ≥3 min; the broader pH 0–8.05; the temperature ≤45°C; initial concentration of residual oil <140 mg/L), which showed a enhancement for the effective adsorption for the residue oil from WWOE.

Fragmentation of chitosan by microfluidization process

Fragmentation of chitosan in 0.1 M acetic acid (HAc) by microfluidization was investigated. The degree of fragmentation was followed by viscometry and size exclusion chromatography. The chemical structure of chitosan and its fragments was examined by elemental analysis and 1H NMR spectroscopy. Fragmentation of chitosan was affected by pressure or intensity of turbulence, exposure time, and hydrodynamic parameters such as molecular weight and polymer concentration in solution; but temperature had only a negligible effect. Chain scission increased bi-linearly with pressure, increased with molecular weight of chitosan but decreased with its concentration. Continuous microfluidization appeared to be more effective in fragmentation than volume pass mode. Molecular weight distribution of fragments was narrower than that of the original polymer indicating that large macromolecules were preferentially fragmented. Degree of acetylation of fragments increased when 0.1 M HAc was used as solvent for chitosan but not in 0.04 M HCl. The fragmentation of chitosan by microfluidization process was described by a parametric model relating chain scission to mechanical action and hydrodynamic parameters of the polymer. It was concluded that microfluidization can be a useful method for moderate fragmentation of chitosan.

Chitosan carboxylic acid salts in solution and in the solid state

When chitosan is associated to simple carboxylic acids, such as formic, acetic, etc., electrostatic interactions occur, resulting in a salt formation, to a greater or lesser degree. Fourier transform infra-red (FTir) spectroscopy and potentiometric techniques were used to characterize the nature of such interactions, in aqueous solutions and in films. The evolution of solid state samples during storage and upon dehydration was studied, by FTir spectroscopy and transmission X-ray diffraction. Results showed that the carboxylic acid content of the films progressively decreased in relation with the physicochemical parameters of the acids (p K a, solubility, etc.). These results were compared with those obtained with a strong acid such as HCl or a complex carboxylic acid (lactic). In X-ray diffraction experiments, three crystalline structures of chitosan were found: a hydrated form, independent of the chemical nature of the salt, and two dehydrated forms depending on the chemical structure of chitosan.