Polyphosphazenes INDEX

Aryloxyphosphazene copolymers can also confer fireproof properties to flammable materials when blended. Dieck [591] have used the copolymers III, and IV containing small amounts of reactive unsaturated groups to prepare blends with compatible organic polymers crosslinkable by the same mechanism which crosslinks the polyphosphazene, e.g. ethylene-propylene and butadiene-acrylonitrile copolymers, poly(vinyl chloride), unsaturated urethane rubber. These blends were used to prepare foams exhibiting excellent fire retardance and producing low smoke levels or no smoke when heated in an open flame. Oxygen index values of 27-56 were obtained. 

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. 

Hydrogels and amphiphilic membranes Poly(carbophosphazenes) and poly(thiophosphazenes) New condensation syntheses NLO and high refractive index polymers Microencapsulation of mammalian cells (PCPP) Polyphosphazene polymer blends and IPN s Borazine derivatives Poly(phosphazophosphazenes)... 

Optical Materials. The polyphosphazene skeleton is electron-rich, which means that it provides a refractive index increment compared to conventional saturated organic backbones. In addition, the macromolecular substitution synthesis aUows highly unsaturated organic side groups to be linked to the skeleton in ways that allow the refractive index, the color, the liquid crystalline, and nonlinear optical characteristics of the polymer to be finely tuned. Thus, the use of these polymers in opto-electronic (photonic) switches and lens systems is a subject of growing interest. 

In 1981 lieu et al at the University of Pittsburgh reported on studies comparing the flammability-toxicity of polyphosphazene and polyurethane foams, using the newly proposed Potential Hazard Index (PHI). In these studies polyphosphazene ranked less hazardous than polyurethane foams. Toxic gases evolved by polyphosphazene included CO, HCN, and NO2, with relative proportions dependant on which formulation was under study (12). 

A number of chlorinated and fluorinated alkoxy- and aryloxy-substituted polyphosphazenes has been prepared in order to investigate the influence of the side-group on refractive index and birefringence. " New polymers with (4-ethyleneoxy)phenoxy side groups (267) as well as polymers with a combination of phenoxy and ethyleneoxy groups (268) have been prepared aiming at... 

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. 

Polyphosphazenes have low inflammability, very high values of limiting oxygen index (LOI) equal to 24-65, and evolve no toxic gases during burning. Most of them do not burn and some are used as additives to other polymers as flame... 

First, the refractive index of a polyphosphazene can be altered by the introduction of side groups that contain different numbers of electrons. High numbers... 

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