Phosphazene Elastomers

Abstract

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.

Rational Design and Synthesis of New Polymeric Material

“…It involves first a ring-opening polymerization of a cyclic six-membered inorganic ring (8) to give a reactive macromolecular intermediate (9), followed by replacement of the chlorine atoms in 9 by reactions with a wide variety of organic, organome- 28 FEBRUARY 1992 SPECIAL SECTION-ARTICLES 7 tallic, or inorganic reagents. Although macromolecular substitution reactions are known for classical organic backbone polymers, the very high reactivity of P-C1 bonds means that the reactions of 9 can be rapid and complete.…”

“…Polymers with mixtures of two or more of these side groups are oil-or flameresistant elastomers, often with surprisingly high flexibility at low temperatures (6)(7)(8)(9)(10). Such elastomers are manufactured cornmercially for use in aerospace, medical, and other advanced applications (10).…”

Phosphazene Polymers: Synthesis, Structure, and Properties

“…Proper selection of reaction time and temperature is necessary to obtain II and avoid the formation of III. For large scale industrial processes, various acids and organometallic compounds can be utilized as catalysts to prepare soluble polymer, both in bulk and in solution (2). The advantages of catalyzed polymerizations include lower reaction temperatures, higher yields, and the use of conventional large scale equipment.…”

“…The polyphosphazenes are long chains of alternating phosphorus-nitrogen atoms with two substituents attached to phosphorus. These polymers have been the subject of several recent reviews (1)(2)(3). Interest has stemmed from the continuing search for polymers with improved properties for existing applications as well as for new polymers with novel properties.…”

Electron beam crosslinking of fluoroalkoxy, methoxyethoxyethoxy, and substituted phenoxy polyphosphazenes: Physical and chemical characterization and comparison to a thermally induced free radical process and ionic complexation

“…The efficacy of electron beam irradiation is assessed and compared to an alternate method, thermally initiated free radical crosslinking. Polymers chosen for these studies include polyfluoroalkoxyphosphazene elastomers PFAP-1 and PFAP-2, 22 MEEP, and PPXP, a mixed phenoxide substituent terpolymer. Additionally, a lithium-MEEP complex was prepared to examine the reported crosslinking effect of metal ions to gain insight into the nature of the crosslink.…”