Side Chain Boron Polymers

The rhodium-catalyzed borylation of alkanes is applied to regiospecific functionalization of polyolefines.165,165a The reaction of polypropylenes (atactic, isotactic, and syndiotactic) with B2pin2 in the presence of Cp Rh( 74-C6Me6) catalyst at 200 °G affords the borylated polymers, which are treated with basic hydrogen peroxide in a mixture of THF and H20 to oxidize the boronate esters to the corresponding alcohols (Scheme 20). The hydroxylated polymers contain 0.2-1.5% hydroxymethyl side-chains. 

In parallel, Scherf et al. [128] have also reported a ladder-type polymer containing carbazole moieties. Their strategy is quite similar to those presented above the authors copolymerized the carbazole moiety with a phenyl bearing two benzoyl side chains. After the polymerization is completed, the ketone moieties located on the phenyl are reduced into alcohol groups by a reaction with MeLi. The ring-closure reaction of the polyalcohol was carried out by treatment with boron trifluoride etherate, affording the ladder polymer. 

A related synthetic strategy by Allcock and Welker65 is illustrated in reaction (19). Here, borazine side groups are linked to a polyphosphazene chain. This reduces the volatility of the borazine and allows facile fabrication of the linear high polymer. Subsequent pyrolysis at temperatures up to 1,000 °C results in breakdown of the phos-phazene carrier backbone (possibly via the formation of volatile phosphorus nitride) and formation of boron nitride. 

Inorganic polymers have backbone chains that do not contain carbon, as organic polymers do, but atoms such as oxygen, nitrogen, phosphorus, boron, silicon, and metals or alternating combinations of them. The side groups attached... 

---