New results of dielectric spectroscopy in semicrystalline nylon-6 samples with different moisture contents are presented by using a wide frequency (10 -2 -3 × 10 6 Hz) and temperature range (133-433 K). The dielectric absorption spectra in frequency domain are decomposed in Cole-Cole distributions corresponding to the local γ and β modes, two segmental R modes, and a high-intensity Maxwell-Wagner-Sillars relaxation. The presence of two segmental relaxations in the isothermal runs, attributed to the plasticized and the unplasticized R mode, is interpreted as the manifestation of two different length and time scales of cooperative motions. A quantitative comparison between the results obtained for the wet and dry samples, such as relaxation times variation, activation energies, Vogel-Tammann-Fulcher parameters, dielectric increments, and distribution widths, is presented for each mode and shows how the progressive drying of the sample during the experiment affects all these quantities.

DC and AC electrical conductivity of bionanocomposites based on the immiscible polymer blend poly(epsilon-caprolactone)/polylactide (PCL/PLA, w/w 70/30), loaded with multiwall carbon nanotubes (CNT), were studied in a wide frequency range, 10(-3) < or = f < or = 10(7) Hz from 143 to 313 K. The nanofiller concentration ranged from 0 to 4 wt % and it was shown to be selectively located in the PCL phase. The PCL crystallinity degree was not affected by the presence of CNT. The variation of the DC conductivity allowed the determination of the percolation threshold, p(c) = 0.98 wt %, and the critical exponent t = 2.2 of the scaling law. The linear dependence of log (sigma(DC)) versus p(-1/3) showed the existence of tunneling conduction among CNT not yet in physical contact. The temperature independent results indicated a conventional tunnel effect. The AC conductivity of the nanocomposites followed the predictions of the universal dynamic response and the s exponents were determined at low concentrations. Master curves are presented showing the length and temperature-time superpositions.

Polycarbonate/poly( -caprolactone) (PC/PCL) blends are found to be miscible when extruded samples are studied without any further thermal treatment. PCL crystallizes in blends containing 60% or less polycarbonate, a component that remains amorphous for all blend compositions under these conditions. Single, broad calorimetric glass transitions together with distinct component dynamics determined by thermally stimulated depolarization current experiments indicate the miscibility of the blends and the existence of different average local compositions. The Lodge-McLeish model is applied to the compositional variation of the two effective glass transition temperatures. Quantitative agreement is obtained for both components by adjusting the self-concentration values to best fit the experimental points. The relevant length for PCL is very close to its Kuhn length, whereas for PC the best fit leads to a slightly shorter characteristic length. It is shown that upon annealing at sufficiently high-temperature PC undergoes crystallization and thereby induces phase segregation in the otherwise amorphous regions of the blends.