The synthesis of a unique class of polymers with a phos phorus-nitrogen backbone is described, focusing on poly-(dichlorophosphazene) and poly(organophosphazene) elastomers. Melt and solution polymerization techniques will be illustrated while briefly indicating the role of catalysts which give significantly improved rates of conversion and reproducibility in polymer properties. The elucidation of chain structure, molecular weight and polymer yield by various dilute solution techniques will be considered.Poly(dichlorophosphazene) is the common, though hydrolytically sensitive, precursor of a large number of poly(organophosphazene) polymers. Examples of tech nologically significant elastomers are shown which are obtained through the use of selected side group substituents attached to the phosphorus-nitrogen backbone. This article concludes with a brief mention of alternate synthetic methods which may lead to useful phosphazene polymers. The study of open-chain polyphosphazenes has drawn increasing attention during the past several years (1-4) • The polyphosphazenes are highly flexible chains of alternating phosphorusnitrogen (P-N) atoms with two substituents attached to phosphorus.Many different polyphosphazenes with a wide range of bulk properties and solubilities have been prepared by varying the type of substituent attached to the P-N backbone. Interest stems from the greater control achieved in the polymerization processes and appreciation of the technological potential of these polymers. This paper updates developments of the past several years (4) with an emphasis on the polymerization process and technological developments of the elastomers. Finally, a brief mention will be made of related polyphosphazenes which currently are attracting interest• NOTE: This chapter is Part II in a series.
The synthesis of a unique class of polymers with a phosphorus nitrogen backbone is described, with an emphasis on poly(dichlorophosphazene) and poly(organophosphazene) elastomers. Poly (dichlorophosphazene) can be prepared by high temperature melt or solution polymerization techniques, with or without the use of catalysts. High performance GPC and other dilute solution techniques have been used to monitor yield and to analyze molecular weight, molecular weight distribution, and chain structure. Although poly(dichlorophosphazene) is an elastomer, it must be modified in order to obtain long term hydrolytic stability and other useful properties. From a common poly(dichlorophosphazene) intermediate, one can introduce a variety of substituents giving polyorganophosphazenes with a wide range of physical properties. Some of the useful properties of phosphazene elastomers and their technological significance will be shown. This article concludes with a brief mention of alternate synthetic methods which may lead to useful polyphosphazene elastomers.The study of open-chain polyphosphazenes has attracted increasing attention in recent years, both from the standpoint of fundamental research and technological development. These polymers have been the subject of several recent reviews (1-6). Interest has stemmed from the continuing search for polymers with improved properties for existing applications as well as for new polymers with novel properties. The polyphosphazenes are highly flexible chains of alternating phosphorusnitrogen atoms with two substituents attached to the phosphorus atom. Although the properties of the polyphosphazenes are influenced to a degree by the molecular weight and chain structure, the properties are determined largely by the size and the nature of the substituent attached to the phosphorus-
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