Chlorinated phosphazenes, structures

In contrast, considering the characteristics of the substituent groups currently used in the chlorine replacements of polydichlorophosphazene, it can be immediately realized that they can be very variable depending on the chemical structure of the nucleophile selected for these reactions. A list of the preferred chemical compounds usually exploited for the phosphazene substitutional processes is reported in Table 4. 

JThe effect of the substituent on the properties of the polyphosphazenes is not fully understood. For instance, [NP(OCH ) ]n and [NP C CH. homopolymers are elastomers (8,29). Synthesis using lithium, in contrast to sodium, salts is claimed to produce rubber-like fluoroalkoxyphosphazene polymers (30). The presence of unreacted chlorine or low molecular weight oligomers can affect the bulk properties (31,32). Studies with phosphazene copolymers both in solution and in the bulk state (29,33-38) indicate a rather complex structure, which points out the need for additional work on the chain structure and morphology of these polymers. 

The modification of lignins with chlorophosphazenes allows the manufacture of products characterized by flame resistance and thermal stability. This can be attributed to the aromatic structure of the lignin-phosphazene polymer as well as to the presence of such flame inhibiting elements as phosphorous, nitrogen and sulfur. Other useful properties may also result from this combination. It has previously been reported (8-13) that the modification provides crosslinked products with suitably low chlorine content. This is a consequence of incomplete substitution of the phosphazenes cycles. Additional modification of the reaction products by chemical compounds with reactive hydroxyl or amine groups reduces the unreacted chlorine content and improves product properties (8-13). Some properties of the derivatives obtained are presented in Table I. 

The introduction of bulky, electron-rich side groups, such as those depicted in structures 3.102-3.105 requires the use of special experimental conditions. If introduced via an aryloxide ion by the macromolecular substitutive route, these side groups impart and suffer considerable steric hindrance. Replacement of every chlorine atom along the phosphazene chain by organic side groups may be difficult. 

Phosphoranimines, which are of interest as monomers in phosphazene polymer synthesis, may be isolated as cationic structures stabilized by donor ligands. In this example, a chlorinated phosphoranimine carrying a hindered aromatic substituent reacts with N,N-dimethylaminopyridine (DMAP) to yield a donor complex. Scheme 4. The donor complex structure was proposed based on single crystal x-ray analysis that revealed a... 

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