Polyphosphazenes hybrid polymers

There have been other types of approaches also for the synthesis of hybrid polymers. Block copolymers containing polysiloxane segments and polyphosphazene segments have been synthesized by the reaction of hydride-terminated polysiloxane H-[Si(Me2)-0]n-SiMe2H with the telechelic polyphosphazene containing an amino end-group (Fig. 6.28) [33]. 

Since both miscible and immiscible phosphazene blends are of considerable interest as membrances, biomaterials, or flame retardant materials, it is worthwhile to study the compatibility of these kinds of blends in more detail in order to understand more about the interaction between the polymer pair and the stability of the blends. Our goal in this study is to prepare PCPP/PS blends and investigate the compatibility and tile properties of the blends by optical clarity, DSC, SEM, FTIR, TGA and LOI. PCPP/PS is chosen in this study because (a) PCPP is known to be flame retardant (5), (b) polystyrene is a well-known versatile organic polymer and has been selected to gi t or blend with phosphazene polymers in most of the polyphosphazene-organic polymer hybrids systems (14,15), and (c) the similarity of aromatic side groups in both of the polymers. In addition, since rcPP has a special thermotropic transition temperature, T(l), and in order to further understand tiie stability of the blends, the compatibility influenced by temperature is also studied before and after T(l) transition by DSC. 

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. 

With this synthetic and molecular structural diversity, polyphosphazene chemistry has developed into a field that rivals many areas of organic polymer chemistry with respect to the tailored synthesis of polymers for specific experimental or technological uses. Indeed, hybrid systems are also available in which organic polymers bear phosphazene units as side groups. This is discussed in another Chapter. 

In addition, the first polythiazylphosphazenes (38), which contain two coordinate sulfur(III) atoms, were prepared from the reaction of Cl2PN2(SiMe3)3 with sulfur halides [50]. The materials, which also possess alternating S-N and P-N units in the polymer backbone, represent true hybrids of poly(sulfur nitrides) and polyphosphazenes and further developments in this area should prove to be particularly interesting ... 

Sulfur-nitrogen-phosphorus polymers possess backbones that can be regarded as compositional hybrids of those present in sulfur-nitrogen polymers, such as the solid-state polymer poly(sulfur nitride) [SNh or polyoxothiazenes [RS(0)=N]n and classical polyphosphazenes, [R2P=N] (1) (92). Poly(sulfur nitride), [SNh, possesses remarkable properties such as electrical conductivity at room temperature and superconductivity below 0.3 K (93). [SNh is insoluble and has a polymeric structure in the solid state with interchain S - S interactions. As these interactions are crucial to the properties of the material, [SNl is best regarded as a solid-state polymer rather than a polymeric material with discrete macromolecu-lar chains of the type discussed in this article. 

Novel MEEP-type polyphosphazene-silicate hybrid network membranes (Tg —38 to 67 °C), exhibiting high ionic conductivities with lithium bis(trifluoromethane-sulfonyl)imide (LiTFSI) as the salt, have been prepared as candidates for dimensionally stable solid polymer electrolytes by a designed sequence of steps starting from [NPCl2] and involving the incorporation and hydrolysis of triethoxysilane groups (Scheme 15). ... 

With the rapid expansion in controlled radical polymerisation chemistry, for example, atom-transfer radical-polymerisation (ATRP) [47], it is clear that combinations with the inorganic polyphosphazene backbone, and its many unique properties, can add extra dimensions and multiply the opportunity for new hybrid materials. As the inorganic component in such polymers is low, often below 5%, the resultant polymers often possess the solution, chemical and biological properties of the attached organic component and can, in effect, be viewed as highly branched versions on an inorganic (potentially degradable) backbone. 

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