Thiophosphazene

Scheme 10 Synthesis of poly(thiophosphazene) and poly(thionyl-phosphazenes)...

The polymerizations of other cyclic phosphazenes have also been studied, including car-bophosphazene, thiophosphazene, and thionylphosphazene [De Jaeger and Gleria, 1998 McWilliams et al., 2000]... 

Closely related to polyphosphazenes is the class of polymers known as polyheterophosphazenes, where one or more of the P atoms per repeat unit is substituted by an atom of a heteroelement. The first well-characterised example of such materials involved carbon as the replacement for phosphorus the resulting macromolecules, polycarbophosphazenes, were prepared via ROP, but at a dramatically lower temperature than for (NPCl2)3 [eqn (11.37)]. Subsequently, polymers with three-coordinate sulfur(IV) and four-coordinate sulfur(VI) centres were obtained and these materials were termed poly-thiophosphazenes and polythionylphosphazenes, respectively. The latter polymers [eqn (11.38)] are much more stable than the sulfur(IV) analogues after halogen replacement and several have been explored as matrices for gas sensors as a consequence of their high permeability. 

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)... 

As discussed in Chapter 3, some other inorganic polymers also contain phosphorus atoms.47 They are derived from the basic phosphazene structure described in Chapter 3, and are obtained by the ring-opening polymerization of heterocyclic compounds in which one of the disubstituted phosphorus atoms is replaced by another moiety. Specifically, introduction of a carbon atom can yield poly(carbophosphazenes), with the repeat unit shown in 6.49. Alternatively, replacement with a sulfur atom can yield a poly(thiophosphazene) (6.50). Relatively little is known about these polymers at the present time 47... 

Values are reported for various poly(thiophosphazenes) ranging from 217 to 330 K, depending on the side groups and molecular weight. ... 

The Staudinger reaction forms also the basis for the preparation of linear oligophosphazenes. The reaction of triphenylphosphine with (19) affords the thiophosphazene (20), which can be converted via (21) into phosphine (22) by subsequent reactions with CF3S03Me and P(NMc2)3. Compound (22) can be... 

The conversion of N3P2SCI5 to its cation implied that ROP can be utilized for its conversion to a linear polymer. This promise was realized much later by the work of Allcock and coworkers [8, 9]. Accordingly, it was found that N3P2SCI5 undergoes a ROP at 90 °C to afford poly(thiophosphazene), [(NPCl2)2(NSCl)]n (see Eq. 5.3). 

P-NMR data and Tg data for some selected poly(thiophosphazene)s are summarized in Table 5.2. The polymer [(NPCl2)2(NSCl)]n has a Tg of -40 °C. Thus, in comparison with [NPCyn the glass transition temperature of... 

The P-NMR data of poly(thiophosphazene)s indicate that the trends observed are similar to those foimd in polyphosphazenes. Thus, while [(NPCl2)2(NSCl)]n shows a resonance at -4.6 ppm, replacing the chlorines by biphenyloxy substituents shifts the P resonance upfield (Table 5.2). 

As mentioned earlier the glass transition temperatures of poly(thionylphosphazene)s indicate that these are polymers with a flexible backbone. These polymers have five side-groups per repeat unit which is similar to poly(carbophosphazene)s and poly(thiophosphazene)s. On the other hand, a comparable polyphosphazene unit has six side-chains. This has interesting consequences on the glass transition temperatures of poly(thionylphosphazene)s (Table 5.3). 

Polymerization of thiophosphazene 116 was conducted in bulk in evacuated Pyrex tubes at 90 °C for 4h. The resulting high polymers (poly-116) show more resemblance to classical polyphosphazenes, but are less stable. ... 

A further variant of this preparative protocol involves the synthesis of polymers that contain phosphorus, nitrogen, and a third element in the main chain. For example, we have recently prepared the first poly(carbophosphazenes) and poly(thiophosphazenes) via the chemistry shown in Schemes III and IV (9, 10), Manners has reported the synthesis of poly(thionylphosphazenes) using the same approach (11),... 

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