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

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

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

Study of dielectric relaxation and dipole moment of some hydrogen bonded solvent binary mixtures in 1,4-dioxane

943-952The dielectric relaxation and dipole moment of different concentration binary mixtures of mono methyl, mono ethyl and mono butyl ethers of ethylene glycol with four polar solvents i.e. ethyl alcohol, glycerol, dimethyl sulphoxide and dimethyl formamide have been measured in dilute solutions of 1,4-dioxane at 35°C. The measured values of permittivity (') and dielectric loss ('') at 10.1 GHz, static dielectric constant (o) at 1 MHz and high frequency limiting dielectric constant (∞) have been used to determine the values of molecular relaxation time ( o), and dipole moment ( ) of the different composition binary mixtures. The analysis of the results based on hetero-association in these binary systems, indicates the existence of different characteristic heterogeneous species in dilute solutions. The comparative values of o and of the various binary mixtures of different composition also suggest that the nature of heterogeneous interaction varies with the type of polar solvent and also constituents composition in the binary mixture

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

Structure and hydrogen bonding in binary mixtures of N,N-dimethylformamide with some dipolar aprotic and protic solvents by dielectric characterization

512-519The low frequency limit static dielectric constant, optical frequency dielectric constant, excess dielectric constant, and the Kirkwood correlation factor of the binary mixtures of N,N-dimethylformamide with water, ethyl alcohol, ethylene glycol, glycerol, dimethyl sulphoxide, acetone and 1,4-dioxane over the entire composition range are investigated at 30oC. The values of these functions emphasize strong N,N-dimethylformamide-water hydrogen bond interaction due to breaking of water tetrahedral structure, whereas the N,N-dimethylformamide-alcohols complexations show a strong hydroxyl group number dependence with enhancement in the structural ordering of alcohols. The dielectric functions of N,N-dimethylformamide-water and N,N-dimethylformamide-1,4-dioxane mixtures reveal the similarity in the complexes, although the N,N-dimethylformamide-water interactions are stronger. The excess functions confirm the weak hydrogen bond interactions of N,N-dimethylformamide with dimethyl sulphoxide and acetone. The pronounced deviation in the excess functions of the studied mixtures confirms the formation of a stable adduct of stoichiometric ratio 1:1 in these systems

Dielectric characterization of solution intercalation and melt intercalation poly(vinyl alcohol)-poly(vinyl pyrrolidone) blend-montmorillonite clay nanocomposite films

196-204Poly(vinyl alcohol) (PVA)-poly(vinyl pyrrolidone) (PVP) blend-montmorillonite (MMT) clay nanocomposite films up to 10 wt.% clay loading were synthesized by aqueous solution intercalation and melt compounding. Complex dielectric function, alternating current (ac) electrical conductivity and complex impedance of these films have been investigated as a function of clay concentration in the frequency range 20 Hz-1 MHz at 30°C. These films show significant decrease in the real part of relative dielectric function (') up to 3 wt. % MMT clay loading and at 5 wt.% their ' values are found to be nearly equal to the PVA-PVP blend film. It is observed that the e¢ values of PVA-PVP blend-MMT clay films are lower than the PVA-MMT clay film at the same clay concentration. The ac electrical conductivity of these films increases with increase of frequency. The dc conductivity of these films varies anomalously with increase of clay concentration. The complex impedance spectra suggest that the dielectric properties of these nanocomposite films are independent of electrode polarization effect in the experimental frequency range. A correlation between dielectric function, structural ordering and the effect of preparation route were explored by considering clay intercalation and exfoliation and the interactions between polymer and MMT clay. This study revealed that the dielectric constant values of these organic-inorganic nanocomposite films can be tuned by loading MMT clay in the polymers matrix, which also improves their physical and thermal properties

Composition- dependent dynamical structures or binary mixtures of mono alkyl ethers of ethylene glycol with some polar solvents determined by microwave dielectric relaxation measurements

891-896The formation of H-bond heterogeneous structures and their dynamics in the binary mixtures of the homologous series of mono alkyl ethers of ethylene glycol with glycerol (Gly), Dimethyl sulphoxide (DMSO) and dimethyl formamide (DMF) have been investigated from dielectric constant and microwave dielectric relaxation measurements at 25oC using Time Domain Reflectometry technique. The concentration dependent values of dielectric constant ant and relaxation time of ethers-Gly mixtures indicate a strong H-bond heterogeneous interaction between the hydroxyl groups of the molecules, and these interactions significantly facilitate the molecular dynamics in the binary mixture, as compared to the dynamics of pure Gly molecules. The dielectric relaxation values of ethers-DMSO and ethers-DMFalso confirm the complex formation in these systems over the entire concentration range. Further, the effect of moleculer size of the ether molecules on the nature of heterogeneous interaction with different polar solvents and hindrance to the molecular dynamics in the binary mixtures has been recognised from the comparative values of measured dielectric parameters