Low-frequency dielectric response and chain dynamics study of poly(vinyl pyrrolidone)–poly(ethylene glycol) coexisting two-phase polymeric blends

317-323The dielectric response of various concentration poly(vinyl pyrrolidone)-poly(ethylene glycol) (PVP–PEG) blends with change in polymer chain-length and their different volume mixtures over the entire concentration range were investigated in the frequency range 20 Hz-1 MHz at 25ºC. The complex dielectric constant ε*(ω), complex electric modulus M*(ω), complex impedance Z*(ω), and a.c. conductivity data were used for the confirmation of the electrode polarization effect, ionic conduction and the micro-Brownian motion of the PVP chain (m-process) in the PVP–PEG blends. All the blends show the dielectric dispersion corresponding to the PVP segmental motion in the upper experimental frequency range whereas in the lower frequency side of the spectra has dielectric dispersion is due to ionic conduction and electrode polarization. The different volume mixtures of some of the different chain-length PVP–PEG blends also shows the polymer chain-length and concentration dependence m-process. All the blends show the d.c. conductivity behaviour in the lower frequency region, which is little affected by the blends composition. The appearance of two separate arcs in the complex impedance plane plots confirms the contribution of nickel-plated cobal electrodes polarization effect to the values of complex dielectric constant of the PVP–PEG blends in the lower frequency range up to 500 Hz

Ionic conduction and dielectric dispersion study on chain dynamics of poly(vinyl pyrrolidone)–glycerol blends

513-520Dielectric behaviour of glass-former polymer blends i.e. poly(vinyl pyrrolidone) (PVP) (average molecular weight Mw= 24000, 40000 and 360000 g mol-1) with glycerol (Gly) up to 30 wt % PVP has been investigated in the frequency range 20 Hz-1 MHz at 25ºC. The frequency dependent complex dielectric constant of the PVP-Gly blends indicates the relaxation process caused by the micro-Brownian chain motion of the PVP in the frequency range 10 kHz-1 MHz. The values of dielectric relaxation strength and relaxation time for this process were determined to explore the concentration and chain length effect on the relaxation process. The ac conductivity values were found corresponding to dc conductivity at frequencies lower than 10 kHz. The loss part of electric modulus exhibits a peak in the frequency range 10 kHz - 40 kHz, which corresponds to the ionic conductivity relaxation. The complex impedance plane plots of PVP-Gly blends confirm the contribution of the electrode surface polarization effect on the dielectric constant values at frequencies lower than 200 Hz. Further, the results of the dielectric dispersion of the PVP–Gly blends were compared with the dielectric dispersion of poly(vinyl pyrrolidone)–ethylene glycol oligomers (PVP–EGOs) blends [Shinyashiki et al., 2006] to confirm the effect of number of hydroxyl groups of the solvent molecules on the heterogeneous hydrogen bond complex formation in these blends

Refractometric study of polymers and their blends in solution

1419-1422Measurement of refractive index (nD) of poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) in solution at 298 K is presented here. PVP has been investigated in nine different polar solvents including liquid PEG200 and PEG400, whereas PVA, PEG, and PVP+PVA and PVP+PEG blend have been investigated in water solution. High frequency limiting dielectric constant (Ɛ∞) has been taken as the square of the measured refractive index (Ɛ∞ =nD²). It is observed that the concentration dependent Ɛ∞ values of these systems exhibit linear behaviour. The Ɛ∞ values of the pure polymers have been determined from the measured Ɛ∞ values of their polymeric solutions. The effect of molecular weight of the polymers on the electronic polarization is discussed by considering comparative Ɛ∞ values of different molecular weight polymers. Results reveal that these polymers and their blends have high solubility in the used solvents, which is mainly due to the polymer-solvent hydrogen bond interactions

Dielectric dispersion and ionic conduction in hydrocolloids of poly (vinyl alcohol)–poly(ethylene oxide) blend–montmorillonite clay nanocomposites

395-402The relative complex dielectric function, electric modulus, alternating current (ac) electrical conductivity and complex impedance spectra of poly(vinyl alcohol) (PVA)–poly(ethylene oxide) (PEO) blend loaded with montmorillonite (MMT) clay nano-platelets up to 10 wt.% in aqueous colloidal suspensions are investigated over the frequency range 20 Hz - 1 MHz at 27oC. The relaxation time corresponding to electrode polarization and ionic conduction processes are determined from the complex spectra of intensive dielectric quantities. The direct current (dc) electrical conductivity of these materials is evaluated by the fitting of real part ac conductivity data to the Jonscher power law, which increases significantly at higher clay concentration. The behaviour of ionic conduction with increase of clay concentration is discussed considering intercalation of the polymers blend in clay galleries with the formation of lamellar nanostructures, and the effect of exfoliated MMT clay nanoplatelets on these structures. Contribution of PVA and PEO on the ionic conduction and electrode polarization phenomena is explored in the hydrocolloids of PVA–PEO blend –MMT clay from the comparative study of various dielectric parameters with the PVA–MMT clay and PEO–MMT clay hydrocolloids