The observation of chain conformation and mobility in polyethylene by solid‐state 13C magic angle spinning (MAS) nuclear magnetic resonance (NMR) permits unambiguous identification and quantitative analysis of an intermediate phase. The carbon‐carbon bonds in the intermediate phase adopt, on the average, an all‐trans conformation and are more mobile than in the crystalline state (room temperature rate of reorientation ≈ 107 Hz). Comparisons of crystallinities by differential scanning calorimetry, wide‐angle x‐ray diffraction, and NMR support the high orientation of the intermediate phase and suggest a lower heat of fusion than for the crystals. Results from 13C spin‐lattice relaxation and 1H spin diffusion show that the mass fractions are ≈ 20% and the domain sizes ≈ 36 Å. Both change with crystallization and annealing conditions. © 1994 John Wiley & Sons, Inc.

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New aromatic poly(amide‐ether)s (II) have been synthesized by solution polycondensation of various aromatic diamines having two ether bridges (I) with a diacid chloride containing silicon, namely bis(chlorocarbonylphenyl)‐diphenylsilane. These polymers are easy soluble in polar amidic solvents such as N‐methylpyrrolidinone or dimethylformamide and can be cast into thin flexible films or coatings from such solutions. They show high thermal stability with initial decomposition temperature being above 400°C. Their glass transition temperatures lie in the range of 220–250°C, except for polymer IIe which did not show a clear Tg when heated in a differential scanning calorimetry experiment up to 300°C. The large interval between the glass transition and decomposition temperatures of polymers Ia–Id could be advantageous for their processing via compression molding. The polymer coatings deposited by the spin‐coating technique onto silicon wafers showed a very smooth, pinhole‐free surface in atomic force microscopy investigations. The free‐standing films of 20–30 μm thickness show low dielectric constant, in the range of 3.65–3.78, which is promising for future application as high performance dielectrics. © 1998 John Wiley & Sons, Ltd.

New aromatic polyamides containing 5-(4-acetoxybenzoylamino) side groups have been synthesized by low-temperature solution polycondensation reaction of equimolar amounts of aromatic diamines having ether bridges with 5-(4-acetoxybenzoylamino)isophthaloyl chloride, in N -methylpyrrolidinone (NMP) as a solvent and in the presence of pyridine as acid acceptor. These polyamides were characterized by IR spectra, viscometry, differential scanning calorimetry (DSC), thermogravimetric analyses and dielectric measurements. These polymers show improved solubility in polar aprotic solvents such as NMP and dimethylacetamide (DMA) and good thermal stability comparable with traditional aromatic polyisophthalamides, with initial decomposition temperature being between 270 and 320 • C and glass transition temperature in the range of 230-270 • C.