Papers by Keyword: Hexanoyl Chitosan

Abstract: Films of hexanoyl chitosan-based polymer electrolytes were prepared using solution casting technique. The interactions between hexanoyl chitosan-lithium perchlorate (LiClO₄) and dimethyl carbonate (DMC)-lithium perchlorate (LiClO₄) were investigated using Fourier transform infrared spectroscopy (FTIR). The FTIR results showed that there is a possible complexation between the electron donor of hexanoyl chitosan and DMC with lithium salt due to the shifting in the wavenumber and changes in the intensity of the infrared bands. The obtained spectroscopic data has been correlated with the conductivity performance of hexanoyl chitosan-based polymer electrolyte. The ionic conductivity was increased with addition of filler TiO₂ and plasticizer DMC to the electrolyte system.

Abstract: Composite polymer electrolytes (CPEs) comprised of hexanoyl chitosan-polystyrene-LiCF₃SO₃-TiO₂ were prepared by solution casting technique. The TiO₂ fillers were treated with 4% sulphuric acid (H₂SO₄) aqueous solution. The effect of treated TiO₂ on the structural and electrical behaviour of the prepared electrolyte systems was investigated by X-ray diffraction (XRD) and impedance spectroscopy, respectively. Addition of TiO₂ decreases the crystallinity of the electrolytes. Ac conductivity was calculated from σ(ω) = ε_oε_rωtanδ. It is found that at all frequencies, σ(ω) increases with increasing temperature. Dielectric constant decreases with increasing frequency and increases with increasing temperature.

Abstract: Hexanoyl chitosan-based polymer electrolytes were prepared using the solution casting technique. The effect of dimethyl carbonate (DMC) plasticizer on the structural and electrical properties of the prepared electrolyte system was investigated by X-ray diffraction and impedance spectroscopy, respectively. Upon addition of 15 wt. % of DMC, the ionic conductivity was increased to 4.09 x 10^-4 S cm^-1 from 3.06 x 10^-4 S cm^-1. The XRD results revealed the variation in conductivity from the structural aspect. For example, sample with lower crystallinity exhibits higher conductivity. The Rice and Roth model was employed to understand the variation in conductivity on the basis of number and mobility of free ions.

Abstract: Hexanoyl chitosan exhibited solubility in tetrahydrofuran (THF) was prepared by acyl modification of chitosan. Polystyrene with molecular weight 280,000 g mol^-1 was chosen to blend with hexanoyl chitosan. LiCF₃SO₃ was employed as the doping salt. Untreated and H₂SO₄ treated TiO₂ was added as the filler. Films of hexanoyl chitosan-polystyrene-LiCF₃SO₃-TiO₂ polymer electrolyte were obtained by solution casting technique. The ac conductivity of the sample was calculated from the relation σ_ac = ε_oε_iω, where ε_o is the permittivity of the free space, the angular frequency, ω=2πf, and ε_i is the dielectric loss. The ac conductivity dispersion observed is analyzed using the Jonshers universal power law, σ (ω) = σ_dc + Aωⁿ where A is a pre-exponential constant and n is the power law exponent with value in the range 0 < n < 1. The temperature dependence of exponent n will then be interpreted using the existing theoretical models.

Abstract: A preliminary investigation of polymer electrolyte based on hexanoyl chitosan, lithium perchlorate (LiClO₄) and various filler additives are described in this paper. Hexanoyl chitosan-based nanocomposite polymer electrolytes were prepared using solution casting technique. The effect of filler addition and type of filler on the electrical properties of the prepared electrolyte system was investigated by impedance spectroscopy (IS). The maximum conductivity of 3.06 × 10^-4 S cm^-1 and 1.96 × 10^-4 S cm^-1 were achieved for the hexanoyl chitosan-LiClO₄-TiO₂ and hexanoyl chitosan-LiClO₄-SiO₂ electrolyte system, respectively. The variations in conductivity observed were discussed quantitatively using the Rice and Roth model from which the concentration of free ions and their mobility were calculated.

Abstract: Films of hexanoyl chitosan-based polymer electrolyte were prepared by solution casting technique. LiCF3SO3, EC and Al2O3 were employed as the doping salt, plasticizer and filler, respectively. The ac conductivity of the electrolyte system under investigation has been studied in the frequency range from 100 Hz to 1 MHz over the temperature range from 273 K to 333 K. The exponent s in the Jonscher’s universal power law equation was analyzed as a function of temperature. The analysis suggests that the conduction mechanism for the nanocomposite electrolyte system can be interpreted based on the correlated barrier hopping (CBH) model. The ac parameters such as the barrier height, WM and cut-off hopping distance, Rmin were calculated. The values of WM and Rmin are found to decrease with increasing temperature in the same manner as the exponent s.

Abstract: Films of hexanoyl chitosan containing lithium perchlorate (LiClO₄) or lithium triflouromethanesulfonate (LiCF₃SO₃) were prepared by solution casting technique. The effect of anion size on the conductivity behaviour of hexanoyl chitosan has been investigated. The conductivity of 4.15 × 10^-7 S/cm and 4.07 × 10^-6 S/cm were achieved for the hexanoyl chitosan-LiClO₄ and hexanoyl chitosan-LiCF₃SO₃ electrolyte system at 50wt.% of salt concentration, respectively. The Rice and Roth model was used to analysis quantitatively the obtained conductivity trends for the prepared electrolyte systems. The diffusion coefficients of cations and anions were calculated from the conductivity and transference number measurements. This is followed by the discussion on the diffusion coefficients of ClO₄^- and CF₃SO₃^- anion.

Abstract: Hexanoyl chitosan: LiClO₄: TiO₂ composite electrolyte films were prepared by the solution cast technique. The ac conductivity and dielectric properties of the samples prepared have been studied in the frequency range from 100 Hz to 1 MHz over the temperature range from 273 to 333 K. The exponent s in the Jonscher’s universal power law, σ(ω)=σ_dc+Aω^s was analyzed as a function of temperature and the analysis suggests that the conduction mechanism can be interpreted based on the correlated barrier hopping (CBH) model. The barrier heights, W_M were calculated. The values of W_M are found to decrease with increasing temperature in the same manner as the exponent s. Both dielectric constant and dielectric loss decrease with increase in frequency and increase with increase in temperature.

Abstract: Hexanoyl chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. The effect of plasticizers on the electrical properties of hexanoyl chitosan: LiCF3SO3 electrolytes have been investigated. The plasticizers used were EC, PC and a mixture of EC and PC. The highest room temperature conductivity of about 1.1 x 10-4 S cm-1 was achieved for electrolyte with composition of 50:50 (wt.%) mixture of PC: EC. The variations in conductivity have been explained using the Rice and Roth model from which the numbers of free ions per unit volume, mobility and diffusion coefficient of free ions were obtained. Electrochemical cells based on LiCoO2/MCMB couple were assembled using the electrolyte that exhibited the highest ionic conductivity. The performance of the cells have been studied and discussed in this paper.