Poly phosphazene copolymers

The phosphazene backbone has a particularly high resistance to thermal treatment and to homolytic scission of the -P=N- bonds, possibly due to the combination of the high strength of the phosphazene bond and its remarkable ionic character [456]. As a consequence, the onset of thermal decomposition phenomena (as detected, for instance, by TGA) are observed at considerably high temperatures for poly[bis(trifluoroethoxy)phosphazene], [NP(OCH2CF3)2]n [391, 399, 457], for phosphazene copolymers substituted with fluorinated alcohols of different length [391, 399, 457], for polyspirophosphazenes substituted with 2,2 -dihydroxybiphenyl groups [458], and for poly(alkyl/aryl)-phosphazenes [332]. 

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]. 

Poly[(4-carboxylatophenoxy)(methoxyethoxyethoxy)phosphazene] copolymers of variable compositions were synthesized by Allcock [645] in 1996. These polymers were found to be soluble in alkaline solutions. When crosslinked (by y-rays or by addition of CaCl2 to the polymer solution) the resulting hydrogels were found able to contract or expand as a function of the pH of the solution and their utilization as pH-responsive materials for drug delivery systems could be envisaged. 

In addition to the termination of living poly(dichlorophosphazene) with phos-phoranimine-terminated poly(dimethylsiloxane), another method has been presented to synthesize poly(phosphazene-siloxane) block copolymers. Hydrosilyla-tion reactions of hydride-terminated poly(dimethylsiloxane) and allyl-terminated polyphosphazenes (210a, 210b) have been shown to yield polyphos-phazene-h/ocfc-polysiloxane-h/oc/c-polyphosphazene polymers (21 la, 21 Ib). ... 

M.C. Ilium, L. Long circulating biodegradable 68. poly(phosphazene) nanoparticles surface modified with poly(phosphazene)-poly(ethylene oxide) copolymer. Biomaterials 1997, 18, 1147-1152. 69. 

Continued commercial interest in poly(phosphazenes) is demonstrated by extensive patent activity and related applications oriented publications (some of which have been noted above). Fire retardency is an ongoing theme in cyclo-and linear phosphazene applications (see section 3). Aryloxy phosphazenes, including a commercial product, Eypel A, have been utilized for components for fire resistance in foam cushioning, rocket motor insulation and electrical wire coating . Alkoxy phosphazene polymers and copolymers impart antistatic properties to silver halide based... 

In vitro evaluations have been made. Bioerodible poly(phosphazenes) have the advantage that the degradation products are biocompatible. The majority of bioerodible poly(phosphazenes) have been synthesized by the classical thermal procedure of Allcock et al. (1965)—reference (15). The copolymer in question is described. In vivo performances in clinically relevant conditions are planned for PPHOS matrices. 

The polymer carbanion can also be used as an anionic initiator for polymerizing a conventional organic monomer to generate a poly-phosphazene-co-organic polymer (Fig. 3.50). The polystyrene graft copolymer prepared as shown above is actually separated into the individual polystyrene and polyphosphazene phases. This is found by the detection of two separate Tg s at +100 °C and +37 °C. 

An interesting example of a phosphazene random copolymer containing thio-phenoxy groups was synthesized by Carriedo and co-workers (76). Although very long reaction times were required and low 5delds (ca 25%) were observed, it was the first time that a thiophenoxy-substituted poly(phosphazene) was obtained. 

One can notice from this table, that these copolymers are usually synthesized with PEG as water-soluble sequences and other biocompatible blocks such as PCL, poly (phosphazene), etc. 

Nonfluorinated ionomer membranes Numerous different types of nonfluori-nated ionomer membranes, among them ionomer membranes based on styrene polymers and copolymers containing polystyrene units [7], arylene main-chain polymers of different poly(phenylene) [8], poly(ethersulfone) [9-11], poly(etherketone) [12-15], poly(phenylene oxide) [16,17], poly(phenylene sulfide) [18] types, and such membranes based on an inorganic backbone like poly(phosphazenes) [19,20], poly(siloxane)s [21], have been developed in the past years... 

Krogman et a/. ° presented the synthesis of blocked poly (phosphazene-l -carbonate)s. First, amino-terminated PTMC was synthesized via ROP. In the synthesis of block copolymers of polyphosphazenes linked to PCs the amino terminus was used to form a covalent link to poly(dichlorophosphazene). 

Vandorpe, J., Schacht, E., Dunn, E., Hawley, A., Stolnik, S., Davis, S.S., Garnett, M.C., Davies, M.C. and Ilium, L. (1997a) Long circulating biodegradable poly(phosphazene) nanoparticle surface modified with poly(phosphazene)-poly(ethylene oxide) copolymer, Biomater.lS 1147-1142. 

AUcock, H. R., Prange, R., Hartle, T. J., Poly(phosphazene-ethylene oxide) di-and triblock copolymers as sohd polymer electrolytes, Macromolecules, 2001, 34, 5463-5470. 

The ability to copolymerize two or more monomers plays a titanic role in property modification in the realm of carbon-based polymers, silicones, and poly(phosphazen-es). We have also found that the co-condmisadon of two N-silyIsaU6nimidates with different R substituents, affords oxothiazene copolymers (equation 7). 

Samples of the poly(dialkylphosphazenes) 1 and 2 displayed X-ray powder diffraction patterns characteristic of crystalline regions in the materials. The peaks in the diffraction pattern of 1 were of lower amplitude and greater angular breadth than those of 2. These data indicate that poly(diethylphosphazene) (2) is highly crystalline while poly(dimethyl-phosphazene) (1) is more amorphous with smaller crystalline zones. This high degree of crystallinity is probably responsible for the insolubility of 2 as noted above. All of the phenyl substituted polymers 3-6 were found to be quite amorphous in the X-ray diffraction studies, a result that is further evidence for an atactic structure of the poly(alkylphenylphosphazenes) 3 and 4 and for a random substitution pattern in the copolymers 5 and 6. 

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