Electrical conduction in polymers under a relatively low applied electric field is considered to be ionic and is affected strongly by the structural factors of the polymers. The following equation for the electrical conductivity σ was derived in which free volume Vf, jump energy Ej, and ionic dissociation energy W were taken into consideration: σ=σ0exp{− [γ Vi*/Vf+(Ej+W/2ε)(kT)−1]}, where σo is a constant, γ the numerical factor to correct the overlap of free volume, Vi* the critical volume required for transport of an ion, ε the dielectric constant, k Boltzmann's constant, and T the absolute temperature. This equation describes well the conduction phenomena in polymethylmethacrylate, polystyrene, and an unsaturated polyester. Relationships between electrical conduction and free volume are discussed.

SynopsisThe annealing effect of ethylene ionomers annealed at various temperatures and for various periods was studied by differential scanning calorimetry. Two endothermic melting peaks were observed for all the ethylene ionomers annealed. The melting peak at the lower temperature, which was assigned to bundlelike crystal owing to a Hoffman-Weeks relationship, shifted to a higher temperature with the annealing temperature and period, indicative of recrystallization.There is physical cross-linking consisting of ionic aggregates, such as multiplets and clusters in ethylene ionomers. The crystallization kinetics of ethylene ionomers was fundamentally similar, but different from that of low-density polyethylene. Crystallization and recrystallization suggested a mobile ethylene chain in both amorphous regions and ionic aggregates even in the presence of cross-linking.

Viscoelastic properties of unsaturated polyesters were investigated in the glass‐rubber transition region in relation to the temperature dependence of specific volume. Polyesters which are homologous with respect to crosslinking density were prepared by using mixtures of succinic and fumaric acid as the dibasic acid component. The temperature dependence of the specific volume was determined by refractive index measurement, the specific refractivity being assumed to be independent of temperature. The temperature dispersion of dynamic viscoelasticity was measured at a constant frequency. Results are summarized as follows. Specific volume and glass temperature are linearly related to the logarithm of crosslinking density. The thermal expansion coefficient and steepness of viscoelastic dispersion decrease with increasing crosslinking density. Fractional free volume and expansion coefficient of free volume, both of which were calculated by WLF equation, are in good agreement with the temperature dependence of specific volume. The results indicate that the effect of crosslinking is largely attributable to the change in amount and distribution of free volume in polymer networks.

Electron‐microscopic texture and physical properties of a styrene–butadiene–styrene (SBS) block copolymer obtained by casting from toluene, carbon tetrachloride, ethyl acetate, and methyl ethyl ketone are discussed. Two peaks are observed in the mechanical loss (tan delta;) curve at −70 and 100°C which are attributed to segmental motion of polybutadiene and polystyrene, respectively. The polybutadiene peak heights are in the order of solubility in the solvent used; the polystyrene peak heights are in converse order. In addition to these peaks, a third peak is observed at 10°C for specimens cast from ethyl acetate or methyl ethyl ketone. A transition corresponding to this peak is also noticed in thermal analysis. It is proposed that aggregation of styrene blocks is relatively incomplete in specimens cast from solution in poor solvents.

Study of the α and β relaxations on a commercial poly(vinyl chloride) by thermally stimulated creep and depolarization current techniquesThermally stimulated depolarization current studies of poly(ethylene oxide) and poly(ethylene oxide) complexed with potassium thiocyanate