Cyclolinear and Cyclomatrix Polymers

Cyclolinear polymers contain cyclophosphazenes as a repeat unit of a polymer chain. Cyclomatrix polymers contain crosslinked cyclophosphazene units. These polymers have not been studied as well as the other members of the phosphazene polymer family. Some of the strategies that have been employed for the preparation of these types of polymers are discussed in this section. The preparation of cyclolinear polymers depends on the design of cyclophosphazene monomers that retain two reactive sites. A few strategies for achieving the synthesis of such monomers are shown in Fig. 4.21 [17], 

The task of preparing appropriate cyclophosphazene monomers for cyclolinear polymers consists of the following. N3P3CI6 consists of six reactive P-Cl units. Clearly this compound as such would not be a suitable monomer for preparing soluble cyclolinear polymers. Recall that condensation polymers involving organic monomers relied on difunctional monomers such as diols, diacids, diamines etc. Replacing four chlorine at- 

Using the above monomers several polymers have been prepared. Thus, monomer 46 has been polymerized by the acyclic diene metathesis polymerization method (ADMET) by using Grubb s catalyst to afford medium-molecular-weight polymers [41]. On the other hand, the reaction of the di-chloro derivative 42 with NaO- C6H4- -S02-C6H4-/7-0Na yields the polymer 49 (Fig. 4.23). Similarly the monomer 47 has been used in condensation polymerization with hexamethylenediisocyanate to afford the polyurethane 50. Polyimides such as 51 have been prepared by using monomer 48. 

Cyclomatrix polymers containing cyclophosphazenes have received some interest. Although N3P3CI6 itself would be an ideal monomer for this purpose as it contains six reactive groups, this has not had much success. 

The utility and practical applications of the cyclolinear and the cyclomatrix polymers have not yet been established and perhaps this would depend on improved design of the cyclophosphazene monomers. 

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The reaction of catechol with N4P4C18 does not give the tetrameric analog of 18 but leads to the degradation of the phosphazene skeleton (17). With diols, such as hydroquinone or resorcinol, cyclolinear and cyclomatrix polymers are formed (21). 

Apart from the mentioned polymers, there are also known cyclolinear and cyclomatrix polymers... 

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