Polyphosphazene chemistry properties

Moreover, the molecular structural, synthetic, and property nuances of these polymers illustrate many of the attributes, problems, and peculiarities of other inorganic macromolecular systems. Thus, they provide a "case study" for an understanding of what may lie ahead for other systems now being probed at the exploratory level. In short, an understanding of polyphosphazene chemistry forms the basis for an appreciation of a wide variety of related, inorganic-based macromolecular systems and of the relationship between inorganic polymer chemistry and the related fields of organic polymers, ceramic science, and metals. 

Such hybrid molecules and supramolecular solids offer the promise of systems with the flexibility, strength, toughness, and ease of fabrication of polymers, with the high temperature oxidative stability of ceramics, and the electrical or catalytic properties of metals. Polyphosphazene chemistry provides an illustration of what is possible in one representative hybrid system. 

Anurima S, Nicholas RK, Swaminathan S, Lakshmi SN, Jacqueline LS, Paul WB, Cato TL, and Harry RA. Effect of side group chemistry on the properties of biodegradable L-alanine cosubstituted polyphosphazenes. Biomacromolecules, 2006, 7, 914-918. 

The development of synthetic routes to new polyphosphazene structures began in the mid 1960 s (2-4). The initial exploratory development of this field has now been followed by a rapid expansion of synthesis research, characterization, and applications-oriented work. The information shown in Figure 3 illustrates the sequence of development of synthetic pathways to polyphosphazenes. It seems clear that this field has grown into a major area of polymer chemistry and that polyphosphazenes, as well as other inorganic macromolecules, will be used increasingly in practical applications where their unique properties allow the solution of difficult engineering and biomedical problems. 

Apart from the ability of PBPP to undergo electroxidation, this polymer is significantly different from previously reported polyphosphazenes, both in preparation and in properties. Although a complete picture of the chemistry of this polymer has yet to emerge, our current progress will be reviewed in the present article. 

As discussed in an earlier section, the chemistry exists to convert hydrophobic polyphosphazenes to materials with hydrophilic surfaces. Hydrogels of MEEP (3.79) have been radiation grafted to the surfaces of hydrophobic polymers to generate highly hydrophilic interfaces, and these systems have the advantage that the interior of the polymer retains its hydrophobicity and other properties, and only the surface layers are changed.187,188... 

Defects in Solids Dielectric Polarizabilities of Oxides Fluorides Diffraction Methods in Inorganic Chemistry Electronic Stmcture of Solids Fluorides Solid-state Chemistry Halides Solid-state Chemistry Intercalation Chemistry Non-crystalUne Solids Oxides Solid-state Chemistry Phosphates Solid-state Chemistry Polyphosphazenes Sol-Gel Synthesis of Solids Solids Computer Modeling Stmcture Property Maps for Inorganic Solids Zeolites. 

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. ... 

The Backbone. The linear inorganic backbone imparts an unusual combination of properties. First, perhaps unexpectedly in view of the unsaturated structure, the skeletal bonds have a low barrier to torsion (perhaps as low as 0.1-0.5KcaF repeating unit), which becomes translated into one of the most flexible backbones known throughout polymer chemistry. This means that some polyphosphazenes have glass-transition temperatures (Tg) as low as -100 °C. It also means that, in the absence of microcrystallinity, numerous polymers of this type are rubbery elastomers. This is a key property for... 

The presence of the phosphorus-nitrogen backbone confers to these kind of polymers thermo-oxidative stability, fire resistance, very high torsional mobility (low barrier to skeletal bond twisting), high refractive index, and hydrophilicity. On the other hand, the side groups in polyphosphazenes control other properties such as solubility, secondary reaction chemistry, thermal decomposition, and resistance to hydrolysis. The possibility of tuning the properties of polyphosphazenes thanks to their synthetic flexibility has led to enormous interest in their applications in several areas of research. 

The derivatization reactions of the poly(alkyl/aryIphosphazenes) afford many new polyphosphazenes with a variety of functional groups and significantly extend the versatility of this class of polymers. Furthermore, the chemistry described above demonstrates that it will be possible to incorporate a number of side-groups into the polymer to enhance the thermal, mechanical, and electrical properties. A large number of graft copolymers of polyphosphazenes should also be accessible via initiation of anionic polymerizations by the polymer anions. 

Polyphosphazenes with fluoro-organic side groups have played a major role in the development of this field. This is a consequence of the unique properties imparted to polyphosphazenes by fluorinated organic groups, but it also reflects the role played by fluorine in the synthesis chemistry as well. There are four ways in which fluorine plays an important role in the synthesis of polyphosphazenes. 

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