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).

Boron-rich boron nitride (BN) films have been prepared on Si and SiO 2 /Si substrates by the vacuum pyrolysis of spin-coated polyborazine films. Physical properties of the prepared films such as film strength, thermal conductivity, and dielectrics were determined. The BN films vacuum-pyrolyzed at 900°C showed residual N-H bonds with a 0.75 N/B ratio, interdiffusion phenomena, and preferred orientation at the interfacial zone. Hardness and the elastic modulus of the film increased to 1.6 GPa and 50 GPa by nanoindentation loading. It had a thermal conductivity of 134 W/(m⅐K) at 296.5 K, and a dielectric constant in the range of 5-7, with tan ٢ between 0.01 and 0.47, depending on the film thickness.

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During the solution reaction of NaBH4/(NH4)2SO4 in tetraglyme to form borazine, polymeric aminoborane (NH2BH2)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 15N and 11B nuclear magnetic resonance firmly proved that the chain‐like poly(aminoborane) evolved a partially condensed B3N3 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 Å. Copyright © 1999 John Wiley & Sons, Ltd.

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