Poly dimethylphosphazene

POLY(DIMETHYLPHOSPHAZENE) AND POLY(METHYLPHENYLPHOSPHAZENE) PoIy[nitrilo(dimethylphosphoranyIidyne)] and PoIy[nitrilo(methylphenylphosphoranylidyne)]  

Submitted by P. WISIAN-NEILSON and R. H. NEILSONt Oiecked by JAMES M. GRAASKAMP4 and BEVERLY S. DUNN4  

alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

As described in the Wilburn procedure, (Me3Si)2NH (104.3 mL, 0.50 mol) and Et20 (500 mL, distilled from CaH2) are placed in a 2-L, three-necked, round-bottom flask that is equipped with a nitrogen inlet, mechanical stirrer, and a pressure equalizing addition funnel fitted with a rubber septum. Then n-butyllithium (n-BuLi) (313 mL, 0.50 mol, 1.6 M in hexane) is transferred to the addition funnel via a cannula and added slowly (—0.5 

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Note All TgS were taken from reference 21 except that for poly(dimethylphosphazene), which comes from reference 81. 

Polysiloxanes are inorganie polymers that eontain alternate silieon and oxygen atoms in their baekbone [1-6]. While the silicon atom has two side-groups the oxygen atom carries none. In this regard they are similar to polyphosphazenes that we have seen in Chap. 3. The most widely studied polymer of this family is poly(dimethylsiloxane) (PDMS) which contains methyl groups as the substituents on silicon. PDMS is isoelectronic with poly(isobutylene) as well as poly(dimethylphosphazene) although its properties are dramatically different (Fig. 6.1). 

The polymerization is in fact a chain-growth reaction and allows access to high molecular weight polyphosphazenes such as poly(dimethylphosphazene) and poly(methylphenylphosphazene) (2). Methyl deprotonation/substitution of these polymers as well as electrophilic aromatic substitution of the phenyl substituents in poly(methylphenylphosphazene) have been developed as versatile strategies for the derivatization of both of these polymers (eq. 3) (3). 

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