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An intrinsically microporous fluoropolymer has been successfully synthesized through thermo-cross-linking of a functional monomer having a quaternary carbon center and thermopolymerizable trifluorovinyl ether groups as the side chains. Because the monomer has a tetrahedral configuration, the thermo-cross-linking produces spontaneously formed micropores with an average size of 8 A in the polymer. Because of the existence of the micropores, the fluoropolymer exhibits excellent dielectric properties with dielectric constant (Dk) of 2.36 and dissipation factor (Df) of 1.29 × 10–3 at a frequency of 5 GHz. Moreover, the polymer shows very low water uptake (

Copolymer ethylene−methyl methacrylate (EMMA) and ultrahigh molecular weight polyethylene (UHMWPE) were blended in decalin solvent. Two kinds of EMMA films with different contents of the MMA side group were used as test specimens. A hot homogenized solution was poured into an aluminum tray to form gels, and the decalin was allowed to evaporate from the resultant gels under ambient condition. Surprisingly, the resultant dry blend films could be elongated up to more than 200-fold (λ = 200) at 135 °C. Such a great draw ratio could be realized even for a blend film with 90% EMMA content (the 9/1 film), although the maximum draw ratio of EMMA homopolymer films was 10-fold (λ = 10). The greatest drawability for the 9/1 films was attributed to large crystal lamellae of UHMWPE, ensuring a crystal transition from a folded to a fibrous type. Accordingly, EMMA chains were independent of the ultradrawing of UHMWPE and kept a random orientation under the ultradrawing process. The storage (Young's) moduli were 20−25 GP...

The relationship between the morphology and the mechanical properties of copolymer ethylene−methyl methacrylate (EMMA) films with different MMA contents was investigated as a function of temperatur...

Hyper-cross-linked polystyrene sorbents with various degree of cross-linking ranging from 25% to over 100% were studied using positron annihilation lifetime (PAL) spectroscopy. Long-lived components of the lifetime distribution of positron annihilation, orthopositronium (o-Ps) lifetimes, give information on the effective size of elementary free volumes (unoccupied spaces), responsible for the properties of sorbents. Experiments were carried out in a vacuum, in air and also in oxygen and nitrogen. Narrow size distribution of elementary free volumes having radius of about 1.5 nm and concentration estimated as ∼1019 cm-3, were found in the samples with cross-linking higher than 40%. Some of the hyper-cross-linked samples gave positronium lifetime τ5 > 50 ns, which is among the highest values ever measured for organic polymer compounds. Positronium quenching (shortening of o-Ps lifetime) due to Ps exchange interaction with oxygen, dissolved in sorbents, gave information about the character of distribution of ...

Three kinds of mechanical relaxations, the α, β, and λ transitions, of ultradrawn polyethylene films were obtained by dynamic mechanical measurements, and the results were analyzed by positron annihilation. The gels were prepared by crystallization from dilute solutions and were then dried. The dried gel films were stretched by up to a draw ratio of 300 times (λ = 300). The temperature dependence of the intensity (I3) of the long-lived component of the orthopositronium (o-Ps) as well as that of the lifetime (λ3) was observed for undrawn and drawn polyethylene films. For the undrawn film, the peak positions of the γ and β transitions corresponded to the first and second transitions of τ3. The β dispersion was not observed for the films with λ = 50 and 300. The second transition of τ3, corresponding to the β dispersion, was observed for drawn films with λ = 50 but was not observed for the film with λ = 300. A histogram of τ3 for three kinds of specimens showed that the size distribution for the undrawn film...