Plastic Carborane

Carborane plastics are produced from the boron molecule (a boron hydride of composition B10FI14) by replacing the four terminal hydrogens with two carbon atoms. The monomer polymerizes at high heat and pressure to form rubbery solids, which will withstand temperatures above 315°C but the commercial plastics are usually copolymers with vinyls, sihcones, or other plastics. Carboranes have been used as specialty adhesives in the aerospace industry. 

To produce elastomeric materials from 95, Kolel-Veetil and Keller studied the effects of reducing the concentration of the diacetylene units in 95 on the plasticities of the resulting networks.127 The ratio (1 2 1) of the carborane, disiloxane, and diacetylene moieties in 95 was altered to 2 3 1, 4 5 1, and 9 10 1, respectively, to produce polymers containing progressively lower amounts of diacetylene units. Two sets of the polymers, one an alternating type (97) and the other a blocky type (98) (Fig. 60), were synthesized. The networked polymers produced from both the blocky and the alternating sets were found to be slightly elastomeric with T values around... 

Figure 64 Hydrosilation reactions between l,7-bis(vinyltetramethyldisiloxyl)-m-carborane monomer and the polymeric cross-linker, poly(methylhydrosiloxane), producing hard, colorless networked plastics. (Adapted from ref. 133.)...

Plastic crystals are almost crystalline solids, except that the molecular constituents in the primitive unit cell rotate freely in place this confers to them a certain degree of plasticity. Examples are certain cage-shaped boranes (e.g., B10H14), carboranes (e.g., Bi0C2Hi2), and buckminsterfullerene (Ceo) at room temperature. These plastic crystals usually order into normal crystalline solids at low temperatures. 

Principal Scientist, GE Plastics, Selkirk, New York Carborane-containing polymers... 

Summary Carborane-hybridized silicon polymers were synthesized from the hydro-silylation reaction between diethynylbenzene-silylene polymers with reactive vinyl side groups and 1,7-bis(dimethylsilyl)carborane and l,7-bis(diphenylsilyl)carborane. Precise NMR spectroscopic studies show that the structures of these polymeres were quite complicated unreacted vinyl groups and pendant carborane substitution exist along with crosslinked carborane. These polymers show plastic moldability. Thermal treatment of the hybrid polymers gives excellent stability in both thermal and mechanical properties of the polymers. Their unreacted moieties seem to act as crosslinkable thermosetting features to make these polymers more stable. 

Our attempt to obtain a silicon-boron hybrid polymer system was successful. Their complicated crosslinkable structure acts as a thermosetting resin to give thermal and mechanical stability with good processability. Carborane hybridization gives exceptional non-flammability. This is a kind of organic-inorganic hybrid system that has plastic versatility and ceramic stability. 

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