Polyphosphazenes living cationic polymerization

Allcock HR, Crane CA, Morrissey CT, Nelson JM, Reeves SD, Honeyman CH, and Manners I. Living cationic polymerization of phosphoranimines as an ambient temperature route to polyphosphazenes with controlled molecular weights. Macromolecules, 1996, 29, 7740-7747. 

Based on the synthesis of polyphosphazenes and of diblock copolyphosp-hazenes by the living cationic polymerization of phosphoranimines [237,241], the triblock poly(phosphazene-ethylene oxide) copolymer XVIII was synthesized by Allcock [223]. 

However, polyphosphazene micelles are known. These are formed by sonication of aqueous suspensions of amphiphilic diblock copolymers—macromolecules in which one block is hydrophilic and the other is hydrophobic. Both blocks may be phosphazene-based, or one block can be a phosphazene and the other an organic polymer. Polymers of this type are assembled via the living cationic polymerization discussed earlier. The polymers shown as 3.95-3.99 illustrate the range of structures that have been studied and the size of the micelles formed.237-240... 

Cationic polymerization of phosphoranimines initiated by small amounts of PCI5 in dichloromethane at ambient temperature offers a new route for the preparation of polyphosphazenes. Initiation of Me3SiNPCl3 gives poly(dichloro-phosphazene) with a narrow molecular weight distribution. The polymerization can be characterized as a living cationic polymerization. ... 

J.M. Nelson, H.R. AUcock, Synthesis of triarmed-star polyphosphazenes via the "living" cationic polymerization of phosphoranimines at ambient temperatures. Macromolecules 30 (6) (1997) 1854-1856. 

Allcock, H. R., Nelson, J. M., Prange, R., Crane, C. A., and de Denus, C. R., Synthesis of Telechelic Polyphosphazenes via the Ambient Temperature Living Cationic Polymerization of Amino Phosphoranimines, Macromolecules, 32,5736,1999. 

These structures are accessible by a variety of techniques that include atom transfer radical polymerization (ATRP) methods and the use of living cationic polymerization. Tri-arm star structures are accessible by the living cationic growth of three chains from a triamino core structure and dendrimers have been obtained by the growth of structures based on a diaminobutane polypropyleneimine core with polyphosphazene outer branches. ... 

FIGURE 1.9 Preparation of a polyphosphazene with one fluorine and one phenyl group on every phosphorus atom using the living cationic polymerization technique. 

FIGURE 1.11 Triblock copolymers containing polyphosphazene units, accessed via the living cationic polymerization method. 

An interesting polyphosphazene derivative, sulfonated poly[bis(2-phen-oxyethoxy)phosphazene], was reported by Paulsdorf et al. [35] (Fig. 7d). Living cationic polymerization of CI3P = NSi(CH3)3 monomer was used to obtain PDCP, which was reacted with 2-phenoxyethanol. The aryl substituents... 

Paulsdorf, J., Buijanadze, M., Hagelschur, K., Wiemhofer, H.D. (2004) Ionic conductivity in polyphosphazene polymer electrolytes prepared by the living cationic polymerization. Solid State Ionics, 169, 25-33. 

Other methods of polyphosphazene synthesis have also been reported [17]. The most interesting is the living cationic condensation polymerization of phosphoranimines [21,22] as it offers access to polyphosphazenes with controlled molecular weight, low polydispersity, and more complex architectures, e.g. block or graft copolymers. At the present time, only moderate molecular weights (Mw = 10 -10 ) are available via the condensation route. 

Later on, such ambient temperature synthesis approach was extended to a variety of organo-substituted phosphoranimines, to directly synthesize polyphosphazenes with controlled molecular weight and low polydispersities, so that PDCP preparation and following chlorine substitution steps were eliminated [26]. Such living cationic condensation polymerization method also allows the preparation of polyphosphazenes with complex structures such as comb, star, and dendritic architectures, as well as block and graft copolymers with organic macromolecules [18]. 

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. 

Cationic condensation polymerizations of Cl3P=NSiMe3 and PhCl2P=NSiMe3 in the solvents benzene, toluene and dioxane, and initiated by PCI5, appear to be reproducible and result in polymers with a low polydispers-ity. Diblock and triblock polyphosphazene-polystyrene copolymers have been synthesized by quenching the living polymer (135) by a polystyrene phos-... 

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