Search

Dielectric spectroscopy (DS) measurements were performed to probe the segmental dynamics and ion mobility of poly(vinyl chloride‐co‐vinyl acetate‐co‐2‐hydroxypropyl acrylate) terpolymer dopped with different amounts of tetrabutylammonium tetrafluoroborate ([TBA] [BF4]) ionic liquid (IL). Differential scanning calorimetry (DSC) was also employed to trace the change in the glass transition temperature (Tg) at different loads of IL. The DSC measurements revealed a remarkable reduction in the PVVH Tg from 344 to 310 K just by adding 20 wt% of IL. The DS measurements revealed three relaxation processes named α, β1, and β2. The α‐process is related to the segmental motion of PVVH while the β1 and β2 are due to the restricted local dynamics of side chains. The segmental relaxation times (α‐relaxation) speed up with increasing the concentration of IL due to the plasticization effect of IL on polymer chains. The temperature dependence of α‐relaxation follows the Vogel‐Fulcher‐Tammann (VFT) relation with dynamic glass transition between 323 and 294 K in agreement with the DSC measurements. The β1 and β2‐relaxations have an Arrhenius temperature dependence. The temperature dependence of ionic conductivity obeys the VFT behavior indicating the coupling between the segmental motion of PVVH chains and ion transport. Polaronic tunneling is the predominant conduction mechanism in PVVH and its composites. The specific capacitance increases with increasing both the temperature and IL concentration. [ABSTRACT FROM AUTHOR]

Polypyrrole/chitosan (PPy/Cs) nanocomposites with various amounts of polypyrrole nanoparticles (PPy‐NPs) have been synthesized and afterwards exposed to UV irradiation for 240 min. Structure, dynamics and antibacterial activity of pure compounds and the corresponding nanocomposites were investigated by means of wide‐angle X‐ray scattering, Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, broadband dielectric spectroscopy and antibacterial activity assay. The occurrence of a pronounced interaction between PPy‐NPs and Cs has been verified. Broadband dielectric spectroscopy measurements revealed two relaxation processes at low and high frequencies. The low‐frequency α‐relaxation associated with the glass–rubber transition is attributed to the presence of hydrogen‐bonded water (plasticizing effect) appearing at low temperature (<373 K). The high‐frequency σ‐relaxation is related to water molecules which become desorbed upon heating at T > 373 K and demonstrates Arrhenius temperature dependence with activation energy in the range 70–90 kJ mol−1 in good agreement with previous reports. On the contrary, PPy‐NPs do not show any structural relaxation process and the charge transport mechanism follows the correlated barrier hopping model. All PPy/Cs nanocomposites exhibit an improved antibacterial activity against both Staphylococcus aureus and Escherichia coli bacteria as compared with pure Cs and PPy‐NPs. © 2018 Society of Chemical Industry Polypyrrole/chitosan nanocomposites with various amounts of polypyrrole nanoparticles have been synthesized and investigated using various methods. The nanocomposites showed high antibacterial activity against both Staphylococcus aureus and Escherichia coli compared with pure chitosan and polypyrrole nanoparticles. [ABSTRACT FROM AUTHOR]