Cyclomatrix polymer

If a cyclophosphazene precursor molecule has more than two reactive sites (e.g. chlorine atoms), linkage reactions with diamines of dialkoxides will generate a three-dimensional structure rather than a linear chain. Such materials are known as cyclomatrix polymers (3.18). These species form a half-way stage between linear polymers and ceramics, and occupy a critical position in materials science. The term ultrastructure covers a broad range of materials of this type. 

The molecular architecture of a polyphosphazene has a profound influence on properties. For example, linear and tri-star trifluoroethoxy-substituted polymers with the same molecular weight (1.2 x 104 or higher) have strikingly different properties.138 The linear polymers are white, fibrous materials that readily form films and fibers, whereas the tri-arm star polymers are viscous gums. One is crystalline and the other is amorphous. Cyclolinear polymers are usually soluble and flexible. Cyclomatrix polymers are insoluble and rigid. Linear polymers can be crystalline, but graft or comb polymers are usually amorphous. 

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). 

N3P3[OC6H3(Bu -3)(OH-4)] (97) by dicarboxylic acid anhydrides or acid chlorides can lead to the formation of cyclomatrix polymers (Section 4). 

Cyclolinear polymers are macromolecules formed by the linkage of intact ring systems, as depicted in IX, whereas cyclomatrix polymers (X) are formed by the three-dimensional crosslinkage of ring systems. 

Linear, branched and cyclolinear polymers are usually soluble. Lightly crosslinked polymers (VII) are swelled by, but are insoluble in liquids. Highly crosslinked or cyclomatrix polymers are insoluble in all media. Oligomers dissolve in liquids to give non-viscous solutions. High polymers dissolve to give highly viscous solutions. 

Introduction.— This section deals only with linear polyphosphazenes neither cyclolinear or cyclomatrix polymers are included, nor is reference made to mixed organic-inorganic polymers. Numerous reviews related to the preparation, physical properties, and application have been published. Readily accessible papers are mentioned here. " ... 

Commercial interest in cyclophosphazenes is demonstrated by the large number of patents involving these materials. Due to its facile thermal, electron beam or photochemical crosslinking to cyclomatrix polymers which forms very hard thin films, the hydroxyethyImethacrylato derivative,... 

Cyclolinear polymers have been evolved with the aim of combining the thermal stability of the phosphazene ring with the flexibility or elastic properties of the chain which Unks them. On the other hand, cyclomatrix polymers contain fully cross-linked rings which are rigid, insoluble, highermelting-point resins of a thermosetting nature. 

Phosphams produced in this manner are believed to be cyclomatrix polymers containing trimeric or tetrameric rings randomly linked by NH bridges into continuous three-dimensional arrays (Chapter 7.2). 

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],... 

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. 

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

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