The dielectric constant, dielectric loss factor, and alternating-current conductivity of Gd-doped poly(vinyl alcohol) (PVA) samples have been studied in the temperature and frequency ranges of 290-450 K and 50-5 3 10 6 Hz, respectively. Three relaxation processes-a a , a c , and q-have been obtained. The first one is due to the rotation of OH and C¼ ¼O groups inside the amorphous part of PVA. The second process is due to the dipole relaxation in the crystalline phase of the sample. The changes in the peak position and height of a a and a c have been interpreted in light of the formation of complexes between GdCl 3 and OH and C¼ ¼O groups of the PVA structure. On the other hand, the q-relaxation process is due to the space-charge formation between the different phases inside the PVA samples. Alternating-current conductivity measurements of the investigated samples have revealed that the hopping conduction mechanism is predominant. The maximum barrier height and the activation energy have been calculated and reported. In the low temperature range (306-333 K), the responsible conduction mechanisms of PVA doped with 2 or 4 wt % GdCl 3 have been found to be small polaron tunneling and quantum mechanical tunneling, respectively.

X-ray diffraction (XRD), dielectric constant (e 0), dielectric loss factor (e 00), and ac conductivity (r ac) of pure and LaCl 3-doped polyvinylidene fluoride (PVDF) have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 140-450 K and 0.1À1000 kHz, respectively. XRD results reveal that pure and LaCl 3-PVDF samples are in the a-phase. The incorporation of La 3þ ions within the PVDF polymer matrix forms complexes which reduce the order structure of PVDF. Three relaxation processes, namely; q, a a , and a c were observed for pure PVDF. The first relaxation can be explained based on space charge formation or Maxwell-Wagner polarization. The second one occurs around the glass transition temperature, T g , and is related to the micro-Brownian motion of the main polymer chain. It becomes broad and shifted to higher temperatures with the doping of LaCl 3. The third process appears below the melting temperature of PVDF and can be attributed to molecular motions of the main polymer chain. The behavior of the ac conductivity shows that the conduction mechanism of pure, 5 wt. % and 10 wt. % of LaCl 3-doped PVDF samples is follows the correlated barrier hopping (CBH) model, while 3 wt. % of LaCl 3-doped PVDF exhibits a small polaron tunneling (SPT) conduction. V

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The dielectric constant (e 0 ), dielectric loss index (e 00 ), direct-current conductivity, and current-voltage (I-V) characteristics of pure poly(vinyl chloride) (PVC) and blends of PVC and bisphenol A/Egyptian corncobs (BCC) were investigated at different temperatures. The relaxation processes for PVC and its blends revealed that PVC and BCC had an incompatible phase. PVC blends with 5 wt % BCC exhibited a peculiar I-V behavior. Both e 0 and e 00 were used to study miscibility and phase behavior in blends of PVC. The activation energies of all PVC samples were calculated. At higher voltages, the conduction mechanism could be identified as the Poole-Frenkel type. In addition, the ionic groups of BCC could enhance the PVC conductivity.

Fourier transform infrared (FTIR) spectrum dielectric constant, e 0 , loss tangent, tan(d), electric modulus, M*, and ac conductivity, r ac , of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La 3þ , Gd 3þ , and Er 3þ ions form complex configuration within PVA structure. Two relaxation processes, namely, q and a were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, a-relaxation process splits into a a and a c . This splitting is due to the segmental motion in the amorphous (a a ) and crystalline (a c ) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping. V C 2012 American Institute of Physics. [http://dx

Poly(3-hydroxybutyrate), PHB, is a widely distributed carbon storage polymer among prokaryotes including Rhizobium. Capacities of Rhizobium etli R13 to produce the bioplastic during growth on media with different carbon sources appeared to be specific carbonsource. In fed batch fermentation, R. etli R13 resulted in cell dry weight 6.2 g/L and PHB 51.4%. Gas chromatography-mass spectrometry and gel permeation chromatography analysis revealed that PHB produced from R. etli R13 was solely composed of 3-hydroxybutyric acid and the molecular mass of the purified PHB was 3.4 Â 10 5 Da with polydispersity 1.47. Dielectric relaxation of PHB has been studied in the temperature and frequency ranges 300-440 K and 10 kHz-4 MHz, respectively. A clear dielectric a and q-relaxation processes are observed in these studied ranges of temperature and frequency. The first process is due to the dipole relaxation in the crystalline phase of PHB. The second one is due to the space-charge formation or Maxwell-Wagner-polarization. The a-relaxation process has been investigated by semiempirical Havriliak-Negami relaxation function. The activation energy (E a ) and the relaxation time (s 0 ) are calculated using the Arrhenius equation. The dielectric relaxation strength (De) is strongly temperature dependent. The calculated values of E a for ac conductivity, ln(r), of PHB provide information about the presence of electronic conduction.

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