Ring-opening polymerization polyphosphazenes

Process III Preparation of Polyphosphazenes by Ring Opening Polymerization Processes of Substituted or Partially Substituted Cyclophosphazenes... 

Three other MEEP-type polyphosphazenes were synthesized by Allcock [622]. Polymers XIII and XIV were prepared via the cationic living polymerization of phosphoranimines, and polymers XV by ring opening polymerization. 

The conventional route to prepare I generally involves a high temperature melt polymerization of hexachlorocyclotriphosphazene, or trimer (IV). Recent studies have demonstrated the effectiveness of various acids and organometalllcs as catalysts for the polymerization of IV (8). Alternate routes for the preparation of chloro-polymer which do not involve the ring opening polymerization of trimer have been reported in the patent literature (9. 10). These routes involve a condensation polymerization process and may prove to be of technological importance for the preparation of low to moderate molecular weight polyphosphazenes. 

It will be clear from the discussion so far that ring-opening polymerization is a crucial step in the synthesis of most polyphosphazenes. Hence, a knowledge of the mechanism of this process is important for widening the scope of this field, optimization of... 

The polymeric phosphazenes are treated in chapter (see Polyphosphazenes) A recent monograph covers the chemistry of polyphosphazenes (nomenclature, synthesis of cyclic monomers , ring opening polymerization, condensation polymerization, substitution, polymer properties, and applications more than 1000 literature citations). Other reviews have also been published recently. Sulfur-containing polyphosphazenes have also been described. ... 

Polyphosphazene is prepared by ring-opening polymerization of hexachloro-cyclotriphosphazene to make a poly(dichlorophosphazene), followed by nucleo-philie substitution reactions to poly(dichlorophosphazene) (Fig. 13.5). Biodegradability and hydrophihc/hydrophobic balance can be controlled by... 

The earliest and most well-developed route to polyphosphazenes involves the thermal ring-opening polymerization of cyclic phosphazenes bearing halogen substituents at phosphorus. Use of this method and subsequent halogen replacement with alkoxides has led to the synthesis of ferrocene- and ruthenocene-containing polyphosphazenes (2.20 and 2.21) with molecular weights (M ) in excess of 2 x 10 [49, 50]. 

The main method of synthesis for polyphosphazenes [4-6] involves the thermal ring opening polymerization of monomer 5 to uncrosslinked high polymer 6, followed by solution state nucleophilic replacement of the chlorine atoms in 6 by organic or organometallic side groups. The overall process is illustrated in Scheme I. 

Silicon polymers and polyphosphazenes are discussed in Chapter 6. It can be argued that they belong in Chapter 4, because they are formed by ring-opening polymerizations. I chose Chapter 6, because silicon polymers can also be formed by reactions other than ring-opening polymerizations. 

These polymers, also called polyphosphazenes, are useful materials when they are substituted with organic compounds [173]. They are prepared from hexachloro-cyclotriphosphazenes by ring opening polymerizations ... 

This polymer was one of the first hydrophobic polyphosphazenes to be synthesized, and it has received by far the most attention. It is produced by the reaction of sodium 2,2,2-trifluoroethoxide with poly(dichlorophosphazene) (4) (Scheme 1), itself prepared by either the ring-opening polymerization of the cyclic trimer,... 

Figure 5.15. Ring-opening polymerization of hexachlorocyclotriphosphazene, and subsequent reactions to yield functionalized polyphosphazenes.

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