Theoretical study of the reaction of chitosan monomer with 2,3-epoxypropyl-trimethyl quaternary ammonium chloride catalyzed by an imidazolium-based ionic liquid

Insights into the interactions between cellulose and biological molecules

Understanding the interactions between carbohydrate polymer molecules and biomolecules is of primary significance for its application. In this paper, the interaction between cellulose and biomolecules was studied using density functional theory method, in which cellobiose, nucleobases, and aromatic amino acids were employed as the structural models of cellulose, DNA, and protein, respectively. Quantitative molecular surface electrostatic potential (ESP) results well represented how cellulose perceived by organism during the recognition. The structural and energetic studies of cellulose with biomolecules complexes show that weak interactions, such as hydrogen bonding interaction, vdW interaction, and pi-H interaction, play an important role in stabilizing these complexes. Through systematic wavefunction analysis, including reduced density gradient (RDG) and natural bond orbital (NBO) methods, the nature of these weak interactions was revealed and further graphically visualized. In-depth understanding of the interaction between cellobiose with biological model molecules may shed lights on the application of carbohydrate polymer-based materials in biological fields.

Studies on Intermolecular Interaction of N-Glycidyltrimethyl Ammonium Chloride Modified Chitosan/N,N-Dimethyl-N-dodecyl-N-(2,3-epoxy propyl) Ammonium Chloride and Curcumin Delivery

Chitosan has potential applications in many fields, due to its biocompatibility, biodegradability and reproducibility. However, the insolubility in water restricts its wide application. In order to expand the application of chitosan in the delivery of oil-soluble drugs and improve the efficacy of oil-soluble drugs, N-Glycidyltrimethyl ammonium chloride-modified chitosan (GTA-m-CS) and N,N-Dimethyl-N-dodecyl-N-(1,2-epoxy propyl) ammonium chloride (DDEAC), a kind of reactive surfactant, were synthesized and characterized by FTIR, NMR and XRD methods. The interactions between GTA-m-CS and DDEAC was studied by surface tension, viscosity, conductivity and fluorescence methods. The parameters, including equilibrium surface tension, critical micelle concentrations of DDEAC with different GTA-m-CS concentration, critical aggregation concentration of DDEAC, the amount of DDEAC adsorbed on GTA-m-CS, pc₂₀ and π_cmc were obtained from the surface tension curves. The influence of temperature on the above parameters were evaluated. The degree of counterion binding to micelle and the thermodynamic parameters of the system were calculated from the conductivity curves. According to the change of conductivity with temperature, the thermodynamic parameters of micellar formation were calculated. The aggregation number of DDEAC molecules in GTA-m-CS/DDEAC aggregates were calculated from steady-state fluorescence data. Based on the experimental results, the interaction models between GTA-m-CS and DDEAC were proposed. The GTA-m-CS/DDEAC aggregates could be used as curcumin carries, and achieved sustained release.

Preparation and Characterization of Electrospun Gelatin Nanofibers for Use as Nonaqueous Electrolyte in Electric Double-Layer Capacitor

A novel nanofibrous gel electrolyte was prepared via gelatin electrospinning for use as a nonaqueous electrolyte in electric double-layer capacitors (EDLCs). An electrospinning technique with a 25 wt% gelatin solution was applied to produce gelatin electrospun (GES) nanofiber electrolytes. Structural analysis of the GES products showed a clearly nanofibrous structure with fiber diameters in the 306.2–428.4 nm range and exhibiting high thermal stability, high tensile strength, and a stable form of nanofibrous structure after immersion in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4). After testing over a range of spinning times, GES electrolytes that were produced at 25 min (GES-25) had a suitable thickness for the assembly of EDLC with the optimized tensile properties and were used to fabricate EDLC test cells with EMImBF4. These test cells were compared to those with pure EMImBF4 and a separator as an electrolyte. The electrochemical properties of the test cells were characterized by charge-discharge testing, discharge capacitance, and alternative current (AC) impedance measurements. AC impedance measurements showed that the test cell with the GES-25/EMImBF4 gel electrolyte showed slightly poorer contact with the electrode when compared to that with pure EMImBF4, whereas exhibited comparable IR drop and discharge capacitance (calculated capacitance retention was 56.6%). The results demonstrated that this novel gel electrolyte can be used as a nonaqueous electrolyte in order to improve the safety in EDLCs.

Preparation of thin-film electrolyte from chitosan-containing ionic liquid for application to electric double-layer capacitors

A novel thin-film electrolyte (TFE) based on chitosan (CS) with 1‑ethyl‑3‑methylimidazolium tetrafluoroborate (EMImBF₄) was prepared by a new procedure for use as a solid electrolyte in electric double-layer capacitors (EDLCs). In this system, EMImBF₄ plays important roles as both a dissolving solution and a charge carrier for EDLC application. By analyzing and characterizing the obtained products, the CS-TFEs showed a surface without CS/EMImBF₄ phase separation and with high thermal stability and good tensile properties. The electrochemical properties were measured as the charge-discharge performance, the discharge capacitance, and alternating-current impedance. A test cell with CS-TFE with a calculated dry thin-film content of 80 wt% EMImBF₄ showed a comparable IR drop and higher discharge capacitance than a liquid-phase EMImBF₄ system and also showed low electrode/electrolyte interfacial resistance. Consequently, this novel CS-TFE is suitable for high-performance EDLCs and improves the safety of such devices.

DFT study on the dissolution mechanisms of α-cyclodextrin and chitobiose in ionic liquid

Density functional theory (DFT) was employed to study the dissolution mechanisms of α-cyclodextrin and chitobiose in 1-ethyl-3-methyl-imidazolium acetate ([Emim][OAc]). Geometrical analysis of the studied complexes indicated that both anion and cation in ionic liquid interacting withα-cyclodextrin and chitobiose contributed to the dissolution reaction. Intermolecular interactions in the complexes were identified as non-covalent interactions, such as hydrogen bonds, van der Waals interactions and repulsions, which were considered as the driving force of dissolution. Among them, hydrogen bonding interactions played a dominant role, which was further visualized in the real space by combination of atoms in molecules (AIM) and reduced density gradient (RDG) techniques. The nature of intermolecular orbital interactions was characterized using natural bond orbital (NBO) theory.