Boron polymer

The most studied class of boron polymers containing boron-silicon bonds are the carboranylenesiloxane polymers. The history of these polymers was discussed at the beginning of this chapter. The more recent advances in this group of polymers and in silicon-containing borazine and boroxine polymers are discussed in later sections of this chapter. In this section, some remaining groups of silicon-containing boron polymers are discussed. 

Wolfe and Wagener have developed main-chain boronate polymers (59) (Fig. 38) by the acyclic diene metathesis (ADMET) polymerization of symmetrical ,oj-dienes, containing both methyl- and phenyl-substituted boronate functionalities using Mo and Ru catalysts.84 The ring-opening metathesis polymerization (ROMP) of several norbornene monomers containing methyl- and phenyl-substituted boronates into... 

Conjugated boron polymers containing platimnn or palladium atom in the main chain were also prepared by hydroboration polymerization between tetrayne/ metal complex monomers and tripylborane (scheme 16).30 From gel permeation chromatographic analysis [THF, polystyrene (PSt) standards], the number-average molecular weights of the polymers obtained were found to be 9000. The polymers were soluble in common organic solvents such as THF, chloroform, and benzene. The absorption peaks due to tt-tt transition were observed around 390 nm in the UV-vis spectra of these polymers. The fluorescence emission spectra exhibited intense peaks at 490 nm in chloroform. 

N. Tanigaki, H. Masude, and K. Kaeriyama, Substituted poly(p-phenylene)s prepared from 2,5-diheptylbenzene-l,4-bis(trimethylene boronate), Polymer, 38 1221-1226, 1997. 

The second reason for interest in boron polymers involves their use as catalysts. While the boron atom can be used as the site of catalytic activity, more effort has been involved in the use of boron-containing materials as blocking and protecting agents, and as cocatalysts. They are increasingly being used in catalytic asymmetric syntheses. 

More recently, we have seen other new plastics arrive, including such exotic, high performance materials as the polybenzimidazoles, polyoxadiazoles, polyperfluorotriazines, polyphenylenes, and such inorganic materials as the boron polymers, the metalloxanes, and the polysilazanes, to name only a few. These exotic materials are mostly development products today, they are very expensive and will undoubtedly find their first uses, if any, in the aerospace industry which requires the high performance offered by these materials and can afford to pay for them. Some of these new materials will become commercial successes, others will not. 

Ruigh, W. L., et al., Research on Boron Polymers, WADC Tech. Rept. 55-26, Parts I-IV. Wright Air Development Center, Wright-Patterson Air Force Base, Ohio. 

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