Boron-containing polymers

A variety of polymers contain the element boron.42,44,52 60 One of the simplest consists of chains of boron fluoride, of repeat unit -BF-, and can be prepared by the reaction of elemental boron with boron trifluoride at high temperatures. The polymer is a rubbery elastomer, but it has been little studied because of its hydrolytic instability and tendency to ignite spontaneously in air.42 However, a variety of other structures are formed with a number of metals, for example chains with Fe, ladders with Ta, sheets with Ti, tetragonal structures with U, and cubic structures with Ca and Ar. Boron also forms chains that are analogues of poly(dimethylsiloxane), with repeat unit -BCH-O-42 

The decabome cage structure has also been used with some comonomers, specifically diamines, to give relatively high molecular weight polymers. Fibers formed from these chains can be pyrolyzed to give products that consist largely of boron nitride, BN. 

The pentaborane cage structure -B5H9- has been used as a side group in the preparation of vinyl-type polymers, but only of relatively low molecular weight. Pyrolysis of this material gives primarily boron carbide, B4C. 

Another example is the poly(borazine) chain, with repeat unit -BRNR-.53,65 The synthesis of tractable, unbranched polymers of this type is complicated by the formation of borazines, which are very stable cyclic molecules, [(RBRN)3], This problem can 

It is also possible to prepare all-carbon polymers of closely related structure. For example, pyrolysis of polyacrylonitrile, (-CH2CHCN-)X, first results in cyclization of some of the -CN side chains.61 Prolonged pyrolysis yields very pure graphitic material. It is very strong and has high thermal stability. In the form of fibers, it can be used for reinforcement in high-performance composites. Additional information on pyrolysis is given in Chapter 9. 

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Air-Stable boron-containing polymers can be prepared by the reaction of dicyano compounds with the / fZ-butylborane—trimethyl amine complex (449). 

Volume 8 Boron-Containing Polymers, edited by Alaa S. Abd-El-Aziz,... 

Macromolecules Containing Metal and Metal-Like Elements, Volume 8 Boron-Containing Polymers, edited by Alaa S. Abd-El-Aziz, Charles E. Carraher Jr., Charles U. Pittman Jr., and Martel Zeldin. Copyright 2007 John Wiley Sons, Inc. 

This low-lying vacant p orbital also allows boron-containing polymers to be luminescent again signaling potential optical applications. Many of these luminescent materials are NLO materials. 

Today, there exist a wide variety of boron-containing polymers including ring systems such as borazines (structure 11.41), boroxines (structure 11.42), and triphosphatoborins (structure 11.43),... 

Abd-El-Aziz, A., Carraher, C., Pittman, C., and Zeldin, M. 2007. Boron-Containing Polymers. Wiley, Hoboken, NJ. 

Ferrocene-Based Polymers, and Additional Phosphorus- and Boron-Containing Polymers... 

This volume of the series focuses on the photochemistry and photophysics of metal-containing polymers. Metals imbedded within macromolecular protein matrices form the basis for the photosynthesis of plants. Metal-polymer complexes form the basis for many revolutionary advances occurring now. The contributors to many of these advances are authors of chapters in this volume. Application areas covered in this volume include nonlinear optical materials, solar cells, light-emitting diodes, photovoltaic cells, field-effect transistors, chemosensing devices, and biosensing devices. At the heart of each of these applications are metal atoms that allow the assembly to function as required. The use of boron-containing polymers in various electronic applications was described in Volume 8 of this series. 

Finally, well-defined boron-containing polymers by dehydrocoupling reactions have been prepared for a hydroboration reaction (Figure 22.7d) [28, 29]. These polymers can be readily obtained in mild conditions without generating water or other by-products. This synthetic route is preferred because it avoids the hydrolysis and disproportionation of boron-containing polymers. Recently we examined a... 

The product is obtained in 95% yield and 94% ee. In the counterpart in solution, the ee was only 21-50%. Polymeric chiral catalysts have also been used in the addition of zinc alkyls to aldehydes. Use of a proline-based copolymer in a continuous asymmetrical synthesis with an ultra filtration membrane gave 80% ee (10.61).138 There was no deactivation in 7 days. A boron-containing polymer (10.62) gave only 28-51% ee compared with the 65-75% ee found with model compounds in solution.139... 

We recently reported the synthesis of transition metal containing polyamides and polyureas [9], utilizing low temperature interfacial and solution techniques. We have now attempted to extend the solution method to the synthesis of boron containing polymers, viz. [lO]. These polymers are of increasing interest as potential precursors for B-N-C type ceramic materials [10], particularly in fiber form. 

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