Polyphosphazenes composites

Homopolymers possess only one type of repeat unit in the chain structure. Thus, except for the chain ends, the composition is constant throughout the chain. It is also possible to prepare chemical copolymers, in which two chemically different repeat units are distributed along the chain backbone. In terpolymers, there are three different types of repeat units. A chemically copolymeric polyphosphazene is shown in Figure 2.17. Thus, copolymers involve a composition variable since, for example, an AB copolymer... 

Examples of known phosphazene polymer blends are those in which phosphazenes with methylamino, trifluoroethoxy, phenoxy, or oligo-ethyleneoxy side groups form blends with poly(vinyl chloride), polystyrene, poly(methyl methacrylate), or polyethylene oxide).97 100 IPNs have been produced from [NP(OCH2CH2OCH2CH2OCH3)2] (MEEP) and poly(methyl methacrylate).101-103 In addition, a special type of IPN has been reported in which a water-soluble polyphosphazene such as MEEP forms an IPN with a silicate or titanate network generated by hydrolysis of tetraethoxysilane or tetraalkoxytitanane.104 These materials are polyphosphazene/ceramic composites, which have been described as suitable materials for the preparation of antistatic layers in the manufacture of photographic film. 

Some of the latest work on high refractive index polyphosphazenes makes use of polymers that contain both fluoroalkoxy and di- or tri-chlorophenoxy side groups.261 These amorphous glasses are thermally stable up to 400 °C, show a large variation of refractive index with temperature, and refractive index values that vary from 1.39-1.56 depending on composition. Thus, they are candidates for uses in thermo-optical switching devices. 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

J. C. Hutchison, R. Bissessur, and D. F. Shriver, Conductivity anisotropy of polyphosphazene-montmorillonite composite electrolytes, Chem. Mater., 8, 1597-1599 (1996). 

Nukavarapu, S.R Kumbar, S.G. Brown, J.L. Krogman, N.R. Weikel, A.L. Hindenlang, M.D. Nair, L.S. Allcock, H.R. Laurencin, C.T. Polyphosphazene/nano-hydroxyapatite composite microsphere scaffolds for bone tissue engineering. Biomacromolecules 2008, 9 (7), 1818-1825. 

FIGURE 11.6 Percentage mass loss versus degradation time (hours) of ethyl glycinato-substituted polyphosphazenes of different compositions in 0.1M sodium phosphate buffer at 37 °C and pH 7.4. The standard deviation (SD) of the mean is less than 3%. Reprinted from Ref. [42] with permission from John Wiley and Sons. 

S. Bhattacharyya, et al.. Biodegradable polyphosphazene-nanohydroxyapatite composite nanofibers scaffolds for bone tissue engineering, J. Biomed. Nanaechnol. 5 (1) (2009) 69-75. 

Y.E. Greish, et al.. Composite formation from hydroxyapatite with sodium and paassium salts of polyphosphazene, J. Mater. Sci. Mater. Med. 16 (7) (2005) 613-620. 

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