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SynopsisThe synthesis and structure of the p-hydroxybenzoic acid polymer is described. The polymer was successfully prepared from either the phenyl ester of p-hydroxybenzoic acid or from p-acetoxybenzoic acid. With highly purified acetoxyben;oic acid, single crystals of the polymer could be prepared. The structure of the polymer was determined and shown to consist of a double helix where the two chains are in a reversed head-to-tail order. The unit cell dimensions are: a = 17.8 8, and c = 18.4 A, where c corresponds to the chain length with a repeat distance of three units. The mechanism of polymerization and formation of the single crystal is discussed. The polymer displays a reversible high-temperature crystalline transition at 325-360°C (not a melting point). The transition was characterized by differential thermal analysis, differential calorimetry, thermal expansion coefficient measurements, high-temperature x-ray scans, and dielectric constant determinations. Orientation of the polymer chains during fabrication and changes in the mechanism of oxidative degradation above the crystal transition are described.

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Activated carbon fibers (ACFs) were oxidized using both aqueous and nonaqueous treatments. As much as 29 wt % oxygen can be incorporated onto the pore surface in the form of phenolic hydroxyl, quinone, and carboxylic acid groups. The effect of oxidation on the pore size, pore volume, and the pore surface chemistry was thoroughly examined. The average micropore size is typically affected very little by aqueous oxidation while the micropore volume and surface area decreases with such a treatment. In contrast, the micropore size and micropore volume both increase with oxidation in air. Oxidation of the fibers produces surface chemistries in the pore that provide for enhanced adsorption of basic (ammonia) and polar (acetone) molecules at ambient and nonambient temperatures. The adsorption capacity of the oxidized fibers for acetone is modestly better than the untreated ACFs while the adsorption capacity for ammonia can increase up to 30 times compared to untreated ACFs. The pore surface chemical makeup was analyzed using elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS).

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During the solution reaction of NaBH 4 /(NH 4 ) 2 SO 4 in tetraglyme to form borazine, polymeric aminoborane (NH 2 BH 2 ) x has been isolated as a white powder. The powder was characterized by thermal gravimetric analysis/differential scanning calorimetry, infrared and mass spectroscopies, and powder X-ray diffraction. Solid-state 15 N and 11 B nuclear magnetic resonance firmly proved that the chain-like poly(aminoborane) evolved a partially condensed B 3 N 3 ring structure by dehydrogenative condensation between chains at 200°C. Pyrolysis of the polymer in a nitrogen stream up to 1400°C led to a 75% yield of hexagonal boron nitride with an interlayer spacing of 3.37 A Ê . Synthesis and Characterization of Poly(aminoborane) / 703 FIGURE 4. Thermal decomposition spectra of poly(aminoborane) for (a) mass 58 mass 73, (b) mass 80 and (c) overall gaseous fragments obtained from mass spectral data. Synthesis and Characterization of Poly(aminoborane) / 707 FIGURE 6. Experimental and simulated 15 N IRCP MAS NMR spectra of the polymer for various inversion time values.FIGURE 7. Evolution versus inversion time of the 15 N IRCP MAS NMR signal intensities of the peaks at À286 and À339 ppm. Curves were ®tted according to equation (1).