Crystallinity Of Chitosan Research Articles

Can Chitosan Be Depolymerized by Thermal Shock?

Chitosan is a biopolymer with a wide range of applications. It typically requires depolymerization to achieve a desired molecular weight for specific uses. This study investigated the potential for depolymerizing chitosan by thermal shock and grinding to produce nanochitosan. A series of thermal shock cycles combined with grinding were performed to assess the influence of drying temperature, residence time, and number of thermal cycles on the molecular weight, particle size, and crystallinity of chitosan. The thermal shock reduced the molecular weight and particle size of chitosan within the first hour of treatment, with optimal conditions achieved at a drying temperature of 90 °C and residence time inside the oven of 5 min. These conditions resulted in a molecular weight of 15.0 kDa with an average diameter of 136 nm. Thermal shock can be considered an effective method for chitosan depolymerization with grinding serving to standardize the particle size. This optimized process offers promising applications where low-molecular-weight chitosan is required, including biomedical, agricultural, and food industries, as well as the potential for reducing time and energy consumption.

Influence of Reduced Graphene Oxide and Carbon Nanotubes on the Structural, Electrical, and Photoluminescent Properties of Chitosan Films.

Chitosan is a biopolymer with unique properties that have attracted considerable attention in various scientific fields in recent decades. Although chitosan is known for its poor electrical and mechanical properties, there is interest in producing chitosan-based materials reinforced with carbon-based materials to impart exceptional properties such as high electrical conductivity and high Young's modulus. This study describes the synergistic effect of carbon-based materials, such as reduced graphene oxide and carbon nanotubes, in improving the electrical, optical, and mechanical properties of chitosan-based films. Our findings demonstrate that the incorporation of reduced graphene oxide influences the crystallinity of chitosan, which considerably impacts the mechanical properties of the films. However, the incorporation of a reduced graphene oxide-carbon nanotube complex not only significantly improves the mechanical properties but also significantly improves the optical and electrical properties, as was demonstrated from the photoluminescence studies and resistivity measurements employing the four-probe technique. This is a promising prospect for the synthesis of new materials, such as biopolymer films, with potential applications in optical, electrical, and biomedical bioengineering applications.

Multifunctional Ag2O/chitosan nanocomposites synthesized via sol-gel with enhanced antimicrobial, and antioxidant properties: A novel food packaging material

In this study, a single step in situ sol-gel method was used to syntheses nanocomposite films using chitosan (CS) as the basis material, with the addition of silver oxide nanoparticles (Ag2O) at several weight percentages (5 %, 10 %, and 15 % Ag2O/CS). The structural characteristics of Ag2O/CS films were investigated using a range of analytical techniques. The presence of the primary distinctive peaks of chitosan was verified using FTIR spectra analysis. However, a minor displacement was observed in these peaks due to the chemical interaction occurring with silver oxide molecules. XRD analysis demonstrated a significant increase in the crystallinity of chitosan when it interacted with metal oxide nanoparticles. Furthermore, it is believed that the interaction between silver oxide and the active binding sites of chitosan is responsible for the evenly dispersed clusters shown in the micrographs of the chitosan surface, as well as the random aggregations within the pores. EDS technique successfully identified the presence of distinctive silver signals within the nanocomposite material, indicating the successful absorption of silver into the surface of the polymer. The developed Ag2O/CS nanocomposite showed promising antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus). Also, Ag2O/CS nanocomposite exhibited marked antifungal activity against Candida albicans, Aspergillus flavus, A. fumigatus, A. niger, and Penicillium chrysogenum. The antioxidant activity of the developed nanocomposite films was studied by ABTS radical scavenging. The highest antioxidant and antibacterial properties were achieved by including 15 % silver oxide into the chitosan. Therefore, our finding indicate that chitosan‑silver oxide nanocomposites exhibits significant potential as a viable material for application in several sectors of the food packaging industry.

Preparation, Characterization, Dielectric Properties, and AC Conductivity of Chitosan Stabilized Metallic Oxides CoO and SrO: Experiments and Tight Binding Calculations.

Polymeric films made from chitosan (CS) doped with metal oxide (MO = cobalt (II) oxide and strontium oxide) nanoparticles at different concentrations (5, 10, 15, and 20% wt. MO/CS) were fabricated with the solution cast method. FTIR, SEM, and XRD spectra were used to study the structural features of those nanocomposite films. The FTIR spectra of chitosan showed the main characteristic peaks that are usually present, but they were shifted considerably by the chemical interaction with metal oxides. FTIR analysis of the hybrid chitosan-CoO nanocomposite exhibited notable peaks at 558 and 681 cm-1. Conversely, the FTIR analysis of the chitosan-SrO composite displayed peaks at 733.23 cm-1, 810.10 cm-1, and 856.39 cm-1, which can be attributed to the bending vibrations of Co-O and Sr-O bonds, respectively. In addition, the SEM graphs showed a noticeable morphological change on the surface of chitosan, which may be due to surface adsorption with metal oxide nanoparticles. The XRD pattern also revealed a clear change in the crystallinity of chitosan when it is in contact with metal oxide nanoparticles. The presence of characteristic signals for cobalt (Co) and strontium (Sr) are clearly shown in the EDX examinations, providing convincing evidence for their incorporation into the chitosan matrix. Moreover, the stability of the nanoparticle-chitosan coordinated bonding was verified from the accurate and broadly parametrized semi-empirical tight-binding quantum chemistry calculation. This leads to the determination of the structures' chemical hardness as estimated from the frontier's orbital calculations. We characterized the dielectric properties in terms of the real and imaginary dielectric permittivity as a function of frequency. Dielectric findings reveal the existence of extensive interactions of CoO and SrO, more pronounced for SrO, with the functional groups of CS through coordination bonding. This induces the charge transfer of the complexes between CoO and SrO and the CS chains and a decrease in the amount of the crystalline phase, as verified from the XRD patterns.

Cobalt oxide-chitosan based nanocomposites: Synthesis, characterization and their potential pharmaceutical applications

This research aimed to prepare, characterize, and investigate the biological efficacy of chitosan‑cobalt (II) oxide hybrid nanocomposites against a variety of micrograms. Analytical methods, FTIR, SEM, XRD, and EDX, were utilized to thoroughly characterize the produced CS-CoO nanocomposite. In FTIR spectra, the presence of the chitosan peaks in addition to that of CoO at 681 and 558 cm−1 confirmed that CoO molecules interact with the chitosan backbone. Moreover, in the XRD measurements, significantly less chitosan crystallinity was observed. Due to the incorporation of a larger amount of cobalt oxide within the polymer matrix. Applying the Debye-Sherrer calculation, the crystallite size was obviously reduced from 48.24 nm (5 wt %) to 19.27 nm (20 wt %) for the obtained nanocomposites. Furthermore, SEM measurements showed a transformation in the chitosan surface with the physical adsorption of CoO molecules on the surface active sites of chitosan that were visible in SEM graphs. Additionally, EDX determined the amount of Co element within the chitosan, with the sample of 20 wt % weight being found to be 19.26 wt %. The variable dose well-diffusion method was utilized to assess the efficacy of the CS-Co nanocomposite against a wide range of bacteria and fungi. CS − CoO nanocomposite is more effective than chitosan alone as an antibacterial agent against both Gram-positive and Gram-negative bacteria. Moreover, the MTT approach was employed to measure the cytotoxicity based on the cell viability of different cancer cell lines under different UV expositions. The proportion of the destroyed cells elevated due to the easy diffusion of CS − CoO nanocomposite into cancer cells as UV-free anticancer activity. UV exposition has stimulated the anticancer activity, which was attributed to an increase in ROS generation caused by the increased dose of the chitosan and its CS − CoO nanocomposites. Furthermore, the antioxidant capacities of the prepared nano-composites thin films were validated using the DPPH free radical scavenging method and showed good antioxidant activities with the DPPH radical compared with standard vitamin C. It has been noticed that by increasing the content of CoO nanoparticles from 5 to 20 wt %, the biological activity of the prepared nanocomposites was enhanced.

Polyelectrolyte Membranes Based on Nafion/Chitosan Blends for Direct Methanol Fuel Cell Application

In this study, polyelectrolyte membranes (PEMs) were fabricated by blending chitosan and Nafion with various compositions for direct methanol fuel cell (DMFC) application. The incorporation of Nafion caused increasing the glass transition temperature (Tg), as well as decreasing the crystallinity of chitosan based matrix, which has roots in the attractive interaction between –SO3H groups in Nafion and –NH2 groups in chitosan structure. In addition, the proton conductivity, as well as the methanol permeability of the studied membranes increased with an increase in the loading weight of Nafion. The selectivity parameter (the ratio of proton conductivity to methanol permeability) of the membrane containing 25 wt% of Nafion was comparable to neat Nafion. In parallel, the results of the DMFC performance test showed a maximum power density of 39 mW cm−2 at 319 mA cm−2 current density (at 5 M methanol concentration and 75 °C) for the mentioned membrane which is near to that for recast Nafion. The results showed that the chitosan/Nafion complex can be considered as a PEM for DMFC application.

FABRICATION OF CHITOSAN BIOPOLYMER FROM PEARL OYSTER SHELLS (Pinctada maxima) FOR MEDICAL APPLICATIONS

Chitosan is one of the biopolymers that has recently been developed in the medical field. Chitosan is biocompatible, biodegradable, and non-toxic, so it is safe for the human body. This study aimed to identify the characteristics of chitosan isolated from pearl oyster shells. Chitosan is obtained through three stages: deproteination, demineralization, and deacetylation. Characterization of chitosan is done physically and chemically including organoleptic test, yield calculation in each step of isolation, FTIR, and XRD. Isolated chitosan identified deacetylation degree and functional group with FTIR. While the crystal structure was determined using XRD. The results showed that chitosan powder has a beige color with a final yield of 7,06%. The characterization of FTIR shows that synthesized pearl oyster shells have successfully formed chitosan compounds with a deacetylation degree of 81,50%. Another characteristic is the crystal structure obtained; chitosan has orthorhombic unit cells with a degree of chitosan crystallinity of 36,94%. Based on the result, chitosan has met several standards in medical applications as a biomaterial.

CHITOSAN FILM COMPOSITE WITH SUGARCANE BAGASSE-DERIVED CELLULOSE FILLER FOR METHYLENE BLUE ADSORPTIVE REMOVAL

Sugarcane bagasse (SCB) was used in this study as a source to produce cellulose (Cell), which was then utilized as filler in modified chitosan (Chi) as a film composite. The purpose of this study was to develop an affordable adsorbent with a high adsorption capability for methylene blue (MB) removal from an aqueous solution, as well as having improved mechanical properties. Based on the result, the tensile strength of chi-cell was increased (from 2.95 kgf/mm2 to 14.50 kgf/mm2 ). Infrared spectra show the intensity of the chi-cell increased in wavenumber 3471 cm-1 , associated with higher abundance of OH groups in the chi-cell which act as active site in the adsorptive removal of methylene blue. According to X-ray diffractogram, the presence of cellulose had no significant effect on the crystallinity of chitosan. TGA data show that cellulose improved the thermal resistance of chi-cell. The adsorption performance of chi-cell reached optimum adsorption after 80 minutes at pH 10. Adsorption was shown to be Langmuir isotherm model dependent (adjusted-R2 =0.998), with Qmax = 3348.14 mg/g.

Chitosan-Strontium Oxide Nanocomposite: Preparation, Characterization, and Catalytic Potency in Thiadiazoles Synthesis.

Recently, Strontium oxide (SrO) nanoparticles (NPs) and hybrids outperformed older commercial catalysts in terms of catalytic performance. Herein, we present a microwave-assisted easy in situ solution casting approach for the manufacture of strontium oxide nanoparticles doped within a naturally occurring polymer, chitosan (CS), at varying weight percentages (2.5, 5, 10, 15, and 20 wt.% SrO/chitosan). To construct the new hybrid material as a thin film, the produced nanocomposite solutions were cast in petri dishes. The aim of the research was to synthesize these hybrid nanocomposites, characterize them, and evaluate their catalytic potential in a variety of organic processes. The strontium oxide-chitosan nanocomposites were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques. All the results confirmed the formation of chitosan–strontium oxide nanocomposite. FTIR spectrum of nanocomposite showed the presence of a characteristic peak of Sr-O bond. Furthermore, XRD revealed that SrO treatment increased the crystallinity of chitosan. The particle size was calculated using the Debye–Scherrer formula, and it was determined to be around 36 nm. The CS-SrO nanocomposite has been proven to be a highly efficient base promoter for the synthesis of 2-hydrazono [1,3,4]thiadiazole derivatives. To optimize the catalytic method, the reaction factors were investigated. The approach has various advantages, including higher reaction yields, shorter reaction durations, and milder reaction conditions, as well as the catalyst’s reusability for several applications.

Photocatalytic Remediation of Harmful Alexandrium minutum Bloom Using Hybrid Chitosan-Modified TiO2 Films in Seawater: A Lab-Based Study

The uncontrolled growth of harmful algal blooms (HABs) can negatively impact the environment and pose threats to human health and aquatic ecosystems. Titanium dioxide (TiO2) is known to be effective in killing harmful algae through flocculation and sedimentation. However, TiO2 in a dispersed form can harm other non-target marine organisms, which has raised concerns by environmentalists and scientists. This research seeks to explore the utility of immobilized titanium oxide as a photocatalyst for mitigation of HABs, where the Alexandrium minutum bloom was used as a model system herein. Chitosan was modified with 0.2 wt.% TiO2 (Chi/TiO2 (x mL; x = 1, 3 and 5 mL) and the corresponding films were prepared via solvent casting method. Scanning electron microscope (SEM) images of the films reveal a highly uneven surface. X-ray diffraction (XRD) analysis indicates the reduction in chitosan crystallinity, where the presence of TiO2 was negligible, in accordance with its dispersion within the chitosan matrix. The photocatalytic mitigation of A.minutum was carried out via a physical approach in a laboratory-scale setting. The negative surface charge of the films was observed to repel the negatively charged A.minutum causing fluctuation in the removal efficiency (RE). The highest RE (76.1 ± 13.8%) was obtained when Chi/TiO2 (1 mL) was used at 72 h, where the hydroxyl radicals generated were inferred to contribute to the deactivation of the algae cells by causing oxidative stress. An outcome of this study indicates that such hybrid films have the potential to replace the non-immobilized (dispersed) TiO2 for HAB mitigation. However, further investigation is required to deploy these films for field applications at a larger scale.

Chitosan sodium benzoate complex as a hydrocolloid and its application for nutraceuticals

Hydrocolloids have been a potential use in food, nutraceuticals, and pharmaceuticals for their viscoelastic properties, such as thickening and gelling. The increasing demand for nutraceuticals and pharmaceuticals has led to the development of new hydrocolloids. Chitosan has been investigated for pharmaceutical excipient, drug delivery agent, and food applications could be a potential hydrocolloid. This study focuses on the physiochemical characterization of chitosan- sodium benzoate hydrocolloid using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). From FTIR and XRD, evident changes were observed in the structure and crystallinity of chitosan- sodium benzoate from chitosan, sodium benzoate, and physical mixture. The thermal decomposition temperatures and weight losses were analyzed using DSC and TGA. In addition to that, antibacterial and antioxidant assays were evaluated.

Crosslinked Chitosan-Gelatin Biocompatible Nanocomposite as a Neuro Drug Carrier.

The polymers, chitosan, a polysaccharide, and gelatin, a protein, are crosslinked in different ratios without the aid of a crosslinking agent. Facile chemical reactions were followed to synthesize a chitosan/gelatin nanocomposite in three different ratios (1:1, 1:3, and 3:1). The solubility of chitosan and the stability of gelatin were improved due to the crosslinking. Both the polymers have excellent biodegradability, biocompatibility, adhesion, and absorption properties in a biological environment. The properties of the composite were favorable to be used in drug delivery applications, and the drug dopamine was encapsulated in the composite for all three ratios. The properties of the chitosan/gelatin nanocomposite and dopamine-loaded chitosan/gelatin nanocomposite were examined using XRD, FTIR, SEM, UV, TGA, TEM, and DLS techniques, and the crosslinking was confirmed. Higuchi kinetic release was seen with a cumulative release of 93% within 24 h for the 1:3 nanocomposite in a neutral medium. The peaks at 9 and 20° in the XRD spectrum confirmed the encapsulation of dopamine with the increase in the crystallinity of chitosan, which is also evident from the SAED image. The dopamine functional groups were confirmed from the IR peaks between 500 and 1500 cm–1 and the wide UV absorption maxima between 250 and 290 nm. The particle size of the drug-loaded composite in the ratios 1:1, 1:3, and 3:1 were calculated to be 275, 405, and 355 nm, respectively. The nanocomposite also showed favorable DPPH antioxidant and antibacterial activity againstStaphylococcus aureus. Sustained release of dopamine in a neutral medium using crosslinked chitosan and gelatin without the presence of a crosslinker is the highlight of the work.

Chitooligosaccharides from shrimp shell chitosan prepared using H2O2 or ascorbic acid/H2O2 redox pair hydrolysis: characteristics, antioxidant and antimicrobial activities

SummaryChitooligosaccharides (COS) prepared from shrimp (Litopenaeus vannamei) shell chitosan using H2O2 at different concentrations or ascorbic acid (AsA)/H2O2 redox pair at various concentration ratios using different hydrolysis times and temperatures were characterised. COS produced by 0.05/0.1 (M/M) of AsA/H2O2 redox pair (COS‐RP) showed higher DPPH and ABTS radical scavenging activities, FRAP, metal chelating activity and ORAC (P < 0.05). Based on fourier transform infrared (FTIR) spectra, COS‐HP and COS‐RP had slight difference between functional groups. COS‐RP had low degree of polymerisation (2–8) and average molecular weight (0.7 kDa). Intermolecular hydrogen bonds were broken, and crystallinity of chitosan was decreased after hydrolysis. COS‐RP showed higher zone of inhibition toward tested bacteria than COS‐HP (P < 0.05). 1H‐NMR and 13C‐NMR spectra also reconfirmed that no drastic alteration in chemical structure of both COS samples took place. Overall, COS prepared using AsA/H2O2 redox pair reaction was recommended due to its higher antioxidant and antimicrobial activities than that using H2O2 alone.

ULTRASONIC ASSISTED SYNTHESIS AND CHARACTERIZATION OF CHITOSAN GRAF WITH 2-(DIMETHYLAMINOETHYLMETHACRYLATE) (DMAEMA) Cs-g-PDMAEMA

Purpose: Many researchers reported the use of chitosan in various applications due to its desirable properties, but then its application in a certain condition is limited due to its lower mechanical stability, lower solubility in certain solvents, and crystallinity of the polymer. Numerous report has been published by many researchers across the world modifying chitosan to enhanced its properties thereby improving its application in various field Methodology: Poly (2-dimethylaminoethyl methacrylate) (Cs-g-PDMAEMA) were successfully synthesized by Ultrasonic methods for the first time. The synthetic method was optimized by varying various reaction parameters and reaction conditions. The grafting was confirmed by characterizing the copolymer with FTIR, XRD, XPS, SEM, TGA, DTG, and DTA. Findings: The results show a good percent grafting and percent yield up to 132%G and 94.7%Y at optimum condition, and also shows a decrease of thermal stability and crystallinity of chitosan, there was improved in porosity of the surface, and complexity of the surface functional group making it a good candidate for metal chelating. Observing various changes in the spectrum of these derivatives and that of pure chitosan in addition to the change in properties of these polymers such as surface morphology, thermal stability, and crystallinity. Uniqe Contribution to Theory, Practice and Policy: It was suggested that this modification may improve the application of these polymers. KeyWords: Chitosan, Cs-g-PDMAEMA, Ultrasonication, Grafting

Solid Dispersion Characteristics of Whiteleg Shrimp (Litopenaeus vannamei) Extracted Chitosan with HPMC and PVP K-30 as Anti-cholesterol Agents

This study aims at evaluating the characteristics of chitosan solid dispersion from whiteleg shrimp (Litopenaeus vannamei). As anti-cholesterol agent, chitosan requires solubility enhancement which can be facilitated in solid dispersion. Here, chitosan solid dispersion was made by solvent evaporation technique used HPMC and PVP K-30 as the carriers, in which the chitosan was prepared from whitleg shrimp shell Chitosan solid dispersion was varied into six formulation, i.e. chitosan: HPMC = FH1 (1:0.25), FH2 (1:0,5), FH3 (1:2), and chitosan: PVP K-30 = FP1 (1:1), FP2 (1:2), and FP3 (1:3), and pristine chitosan, HPMC, and PVP K-30 were utilized as reference compound. Characteristics of chitosan solid dispersion were assessed from the solubility test, SEM, XRD, and FTIR. The result indicates that solubility of chitosan solid dispersion was better than the pristine chitosan. The recommended formula from this study was FP3, because obtained smaller particle size than the other, that could increase the solubility of chitosan. The crystallinity of chitosan remained unchanged upon solid dispersion preparation.

Magnetic Sulfonated Chitosan composite beads for Mercury removal from Aqueous solutions

Magnetic sulfonated chitosan composite beads had been prepared and applied for mercury removal from aqueous solutions. Preparation of magnetic sulfonated chitosan composite beads was initially performed by the sulfonation of chitosan and continued with the addition of iron oxide particles prepared from local iron sand to form composite beads. The magnetic sulfonated chitosan beads were characterized by FTIR and XRD analysis. FTIR spectra confirmed the formation of magnetic sulfonated chitosan beads. The patterns of XRD exhibited the decrease of chitosan crystallinity after modification. The result of adsorption experiments showed that the addition of sulfonation and iron oxide particles can improve the adsorption capacity of chitosan.

The effect of amino acids extracted from tofu wastewater on chitosan performance for methylene blue removal from water

In this study, we have modified chitosan using amino acids to form a chitosan-amino acid film. Amino acids were extracted from the tofu wastewater of the tofu producer, Timbul Jaya in Banda Aceh. The amino acid loaded on chitosan was varied (1, 0.5, 0.25, and 0.1 mL). The best chitosan-amino acid films were obtained at 0.5 mL amino acid loading. Chitosan-amino acid films were characterized using XRD (X-Ray Diffraction), TGA (Thermogravimetric Analysis), DSC (Differential Scanning Calorimetry), and FT-IR (Fourier Transform Red Spectroscopy). XRD data showed that amino acid loading did not affect the crystallinity of chitosan. Based on TGA and DSC data, the addition of amino acids slightly decreased the thermal properties of chitosan. FTIR data confirmed the amount of amino acids loaded can increase the amine group in chitosan. Adding amino acids to chitosan film was able to increase the adsorption capacity of chitosan.

Preparation and characterisation of chitosan extracted from shrimp shell (Penaeus monodon) and chitosan-based blended solid polymer electrolyte for lithium-ion batteries

A bioactive and non-toxic biopolymer-based electrolyte has gained attention in recent research for their potential applications in the fabrication of electrochemical devices. In this work, we extracted the chitosan successfully prepared from shrimp shells using Brine’s method. The solid polymer electrolyte comprising the blend of chitosan and agar–agar, plasticised with polyethylene glycol (PEG), as host polymer and lithium perchlorate (LiClO4) as a dopant is prepared by solution casting technique. Also, the effect of different weight percentage of the plasticiser PEG at a fixed ratio of perchlorate content is investigated. The obtained chitosan blended film is highly suitable as a electrolyte for electrochemical devices. The prepared polymer electrolyte is characterised using attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR), high-resolution scanning electron microscopy (HR–SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy. The ATR–FTIR spectroscopy confirms the presence of particular functional groups present in chitosan and complex formation between blended polymers and lithium perchlorate. The surface morphology and amorphous crystallinity of chitosan and blended polymer electrolytes revealed from HR–SEM and XRD analysis. The ionic conductivity of the prepared materials is studied using AC impedance spectroscopy and compared. The highest ionic conductivity at room temperature obtained for the sample is 4.56 × 10−4 Scm−1 (CAP3). The mechanical properties of films have been studied using a Universal testing machine analysis. Wagner’s polarisation measurements have estimated the Li+ transport numbers of SPEs. Linear sweep voltammetry was performed on half-cell method to study the electrochemical stability window of the maximum ionic conductivity of SPEs.

Graphene oxide enhanced ionic liquid plasticisation of chitosan/alginate bionanocomposites

The effect of graphene oxide (GO) or reduced GO (rGO) on the structure and properties of polyelectrolyte-complexed chitosan/alginate bionanocomposites is highly dependent on plasticiser type (glycerol or 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])) due to the competing interactions between the components. For the glycerol-plasticised chitosan/alginate matrix, inclusion of GO/rGO enhanced the chitosan crystallinity and increased matrix ductility. While the chitosan/alginate matrix plasticised by [C2mim][OAc] showed dramatically weakened interactions between the two biopolymers, GO was highly effective at counteracting the effect of [C2mim][OAc] by interacting with the biopolymers and the ionic liquid ions, resulting in enhanced mechanical properties and decreased surface hydrophilicity. Compared with GO, rGO was much less effective at promoting chitosan–alginate interactions and even resulted in higher surface hydrophilicity. However, irrespective of the plasticiser type, inclusion of rGO resulted in reduced crystallinity by restricting the interactions between [C2mim][OAc] and the biopolymers, and higher ionic conductivity.

Evaluation of chitosan crystallinity: A high-resolution solid-state NMR spectroscopy approach

We propose a novel approach relied on high-resolution solid-state 13C NMR spectroscopy to quantify the crystallinity index of chitosans (Ch) prepared with variable average degrees of acetylation (DA¯) from 5% to 60 % and average weight molecular weight (M¯w) ranged in 0.15 × 106 g mol−1–1.2 × 106 g mol−1. The Dipolar Chemical Shift Correlation (DIPSHIFT) curve of the C(6)OH segment revealed increased mobility dynamic, which induced different distribution from trans-to-gauche conformations in relation to C(4). Indeed, 1H-13C Heteronuclear Correlation (2D HETCOR) showed that distinguished C4 chemical shifts correlates with the same aliphatic protons. The short-range ordering can be assigned to C4/C6 signals on 13C CPMAS and, for our case, the deconvolution procedure between disordered and ordered phases revealed increasing crystallinity with DA¯, as confirmed by SVD multivariate analysis. This work extended the knowledge regarding the use of 13C CPMAS technique to predict the crystallinity of chitosans without the use of amorphous standards.