Phosphazenes. See

The decrease in the SiOSi angle in trimeric (OSiMe2)3 from its optimum value of about 145°, as well as the nearly planar geometry of the cycle, probably are related to the strained character of the ring. Similar effects operate in the case of phosphazenes (see above). 

For a recent analysis of the bonding in phosphazenes, see V. Luana, A.M. Pendas, A. Costales, G.A. Carriedo and FJ. Garcia-Alonso... 

As regards photoconducting polymers, typical work has been carried out with poly(N-vinylcarbazole), PVK, and polysilylenes. The first commercial photoconductor was based on a 1 1 charge-transfer (CT) complex between PVK and trini-trofluorenone (TNF) [11]. Similar photoconductor properties were found with a 1 1 CT complex of TNF with poly[bis(2-naphthoxy)phosphazene] (see Chart 2.7), which is an insulator if dopant-free [54]. 

The phosphoranimine approach can also be used to prepare poly-(fluoro/aryl)phosphazenes (see Eq. 3.61) [34]. 

Poiyphosphazene Biends Blends of sulfonated polyphosphazene, for example, sulfonated poly[bis(3-methylphenoxy)phosphazene] or poly[(bisphenoxy)phosphazene] (see Fig. 29.14) with either an inert organic polymer such as poly(vinylidene fluoride) (Pintauro and Wycisk, 2004 Wycisk et al., 2002) or polyacrylonitrile (Carter et al., 2002) or a reactive polymer (e.g., polybenzimidazole) (Wycisk et al., 2005) have been investigated. The resultant membranes had conductivities of 0.01-0.06 S/cm (in water at 25°C) and equilibrium water swelling from 20 to 60% (at 25°C). Blends of poly[(bisphe-noxy)phosphazene] and polybenzimidazole (where acid-base complexation occurred between the sulfonic acid and the imidazole nitrogen) exhibited good mechanical properties and low methanol permeability. MEAs with this membrane material outperformed Nafion 117 in a DMFC at 60°C with concentrated (5-10 M) methanol feeds. With 1.0 M methanol and 0.5 L/min ambient air at 60°C, the maximum power density was 97 mW/cm and the methanol crossover was 2.5 times lower than that with Nafion 117 (Wycisk et al., 2005). 

Applications. Among the P—O- and P—N-substituted polymers, the fluoroalkoxy- and aryloxy-substituted polymers have so far shown the greatest commercial promise (14—16). Both poly[bis(2,2,2-trifluoroethoxy)phosphazene] [27290-40-0] and poly(diphenoxyphosphazene) [28212-48-8] are microcrystalline, thermoplastic polymers. However, when the substituent symmetry is dismpted with a randomly placed second substituent of different length, the polymers become amorphous and serve as good elastomers. Following initial development of the fluorophosphazene elastomers by the Firestone Tire and Rubber Co., both the fluoroalkoxy (EYPEL-F) and aryloxy (EYPEL-A) elastomers were manufactured by the Ethyl Corp. in the United States from the mid-1980s until 1993 (see ELASTOLffiRS,SYNTHETic-PHOSPHAZENEs). 

See Elastopiers.synthetic-phosphazenes Inorganic high polymers. 

Not inclusive see also Acrylic elastol rs, Phosphazenes, Cm OROSULFONATED polyethylene, Eethylene-acrylic elastot rs, Polyethers under the tide ElASTOT RS, SYNTTiETIC. 

ETP2 base, see phosphazene base 2 Evans auxiliary, see Darzens reaction 13 exo cyclization mode 272... 

The true value of the chloropolymer (I) lies in its use as an intermediate for the synthesis of a wide variety of polytorgano-phosphazenes) as shown in Figure 1. The nature and size of the substituent attached to the phosphorus plays a dominant roll in determining the properties of the polyphosphazene. Homopolymers prepared from I, in which the R groups are the same or, if different, similar in molecular size, tend to be semi-crystalline thermoplastics. If two or more different substituents are introduced, the resulting polymers are generally amorphous elastomers. (See Figure 1.)... 

MYKONOS wind-mills (see below) the first figure refers to the munt r of atoms within the phosphazenic ring (6 = N3P3, 8 = N P ) and the second figure is connected with the number of atoms within the cyclic amino ligand (3 = Az, 5 = Pyrro). 

These new, uncharged amine bases are strong enough (pXa of 4 in acetonitrile is 42.62) to deprotonate esters or lactones, where they can even be used with advantage over the more conventional bases like LDA or metal hcxamethyldisilazanides. For example, the alkylation of dimethyl isopropylidene tartrate with n-alkyl iodide is not possible with the latter bases but can be achieved with phosphazene-base P4-t-Bu or phosphazene-base P4-t-Oct24. With phos-phazene-base P4- -Bu the yield of 8 is 41 % with 28 % of recovered starting material 6, whereas with phosphazene-base P4-i-Oct the yield of 8 is 71 % with only 9% of 6 left unreacted. (For alkylations of 6 with other more active electrophiles see later.)... 

---