Spectroscopic and thermal analysis of polyacrylamide/chitosan (PAM/CS) blend loaded by gold nanoparticles

Different concentrations of gold nanoparticles (Au NPs) have been doped to polyacrylamide/chitosan (PAM/CS) blend by casting method to demonstrate the effect of nano particles as a doped on the structural, morphological and thermal behavior for PAM/CS blend. Nanocomposite films were characterized before and after addition of the gold. The FT-IR measurement shows some changes in the chemical structure with increase of the gold nanoparticles. The X-ray diffraction indicated that degree of crystallinity for PAM/CS blend was decreased after adding the nano-gold. Transmission electron microscope (TEM) images of the samples contain the gold nanoparticles in PAM/CS matrices showed that the spherical particle has a size range nearly from 5 to 30 nm. The parameters of kinetic thermodynamic like activation energies, enthalpy, Gibbs free energy and entropy were calculated from the thermogravimetric (TG) curves. The thermal data irregularly decrease with increasing of gold nanoparticles. TG analysis showed the thermal stability of nanocomposites films after addition of Au NPs was enhanced. Keywords: PAM/CS blend, Gold nanoparticles, FT-IR, X-ray, TEM, T

Influence of Cr2O3 Nanoparticles on the Structural, Optical, Thermal and Electrical Properties of PEO/CMC Nanocomposites

Abstract In the present paper, different concentrations of chromium oxide (Cr2O3) nanoparticles were incorporated within PEO/CMC polymer blend to produce nanocomposite films using the casting method. The X-ray diffraction was performed on PEO/CMC-Cr2O3 nanocomposites. The main X-ray peaks of Cr2O3 were observed and defined as cubic structure and orthorhombic shape with an average particle size of the Cr2O3 ~ 50-80 nm. The decrease of some IR bands after the addition of Cr2O3 nanoparticles was found attributed to the interactions between PEO/CMC and Cr2O3. Effect of Cr2O3 nanoparticles on optical properties such as absorbance and optical energy gap (Eg) were characterized using UV-Vis spectroscopy. The Eg was reduced after the addition of Cr2O3 nanoparticles. The AC conductivity (sac), dielectric constant (ε′), dielectric loss (ε′′) and the dielectric modulus (M′ and M′′) were calculated at frequency range 0.1 Hz-7 GHz. The increases of direct conductivity (σdc) imply that the free charge density or of the charge mobility that results. The estimated values of both ε′ and ε′′ were decreased with increases of frequency. The addition of Cr2O3 nanoparticles causes the formation of a charge-transfer complex. The Cole-Cole plot between (M′ and M′′) shows a semi-circular shape confirm discuses according to a non‐Debye method.</jats:p

Verification of the changes in the structural and physical properties of PU/PEO embedded with graphene oxide

Blend of polyurethane (PU) and polyethylene oxide (PEO) doped graphene oxide (GO) was prepared and investigated. The main bands of GO were increased with increasing of graphene contents due to oxidant induced chemical attachment of PU/PEO chains to the surface of GO. IR bands were increased attributed to oxidant-induced chemical attachment between GO and PU/PEO chains. The shift in TGA curves toward higher temperatures than that of PU/PEO which indicate the thermal stability of the samples. The activation energy was increased implying a variation of reactivity as a result of the extent reaction. Moreover, the kinetic parameters ΔS, ΔH and ΔG indicate that the addition of GO cause increase of thermal motion and decrease of the thermal stability. On the other hand, the behavior of ε′ and ε″ curves was decreased at low frequency and become nearly constant at the higher frequency due to the relaxation time. At low frequencies, the electric dipoles have enough time to align with field however at high frequencies attributed to shorter time available for dipoles to align after a rise of the field. A rise for M′ and M″ at the range of higher frequencies due to bulk effect suggesting polarity of relaxation mechanism. Keywords: Nanocomposite, Graphene oxide, Raman shift, FT-IR, TGA, Kinetic parameter

Thermal Spectroscopy and Kinetic Studies of PEO/PVDF Loaded by Carbon Nanotubes

Nanocomposites of polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF) without and with low content of single and multiwalled carbon nanotubes (SWCNTs-MWCNTs) were prepared and studied by thermogravimetric analysis (TGA) using different heating rate. TGA results indicate that the thermal stability of neat PEO/PVDF blend was improved with both heating rate and incorporation of carbon nanotubes (CNTs). The degradation temperature for neat blend was lower than those of the nanocomposites after adding both SWCNTs and MWCNTs. As increase of heating rate, the onset of decomposition is irregularly moved to higher temperatures. This indicates that the thermal stability of the polymeric matrices has been improved after addition of CNTs. The residual weight of the samples left increased steadily with adding of both SWCNTs and MWCNTs. Kinetic thermodynamic parameters such as activation energy, enthalpy, entropy, and Gibbs free energy are evaluated from TGA data using Coats-Redfern model. The values of all parameters irregularly decrease with increasing of heating rate due to increasing of heating rate temperature, the random scission of macromolecule chain in the polymeric matrices predominates and the activation energy has a lower value

Raman, morphology and electrical behavior of nanocomposites based on PEO/PVDF with multi-walled carbon nanotubes

AbstractIn this work, FT-IR, Raman, TEM spectroscopy and AC conductivity were used to study and characterize of PEO/PVDF blend incorporated with low content of multi-walled carbon nanotubes (MWCNTs). Main characteristics of IR and Raman bands for the two polymers and MWCNTs were observed. The shift of G, D and G″ bands of MWCNTs occurred. All results showed that MWNTs-COOH were covalently linked with the blend through OH and C–C bonds. TEM images illustrated that MWNTs were well dispersed into polymeric matrices and wrapped with PEO/PVDF chains. The temperature dependent conductivity measurements of nanocomposites were studied. The addition of MWCNTs increases and enhances the conductivity attributed to charge carrier build up and increases in segmental mobility of polymeric chains. Molecules in the loaded samples begin to bridge the gap which separates them by lowering potential barriers and the localized state between them. Values of both ε′ and ε″ are high at lower frequency and decrease with an increase of frequencies due to polarization effects