Carbophosphazenes

The poly(carbophosphazenes) that have been synthesized are amorphous rather than crystalline, and they appear to retain the same atom sequencing along the chain as in the cyclic trimer from which they are derived. Hence, repeating group scrambling during polymerization does not appear to be a significant component of the process. 

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... 

Cl N Cl This polymer is the first example of a poly(carbophosphazene). 

The six-membered heterocyclic ring, cyclocarbophosphazene, [(NPCl2)2CCl] serves as the precursor for poly(carbophosphazene)s. The pentachlorocyclocarbophosphazene N3P2CCI5 can be considered as a hybrid of cyanuric chloride, N3C3CI3 and hexachlorocyclotriphosphazene, N3P3CI6. Thus, while cyanuric chloride has three carbons and the hexachlorocyclotriphosphazene has three phosphorus atoms, the cyclocarbophosphazene has one carbon and two phosphorus atoms (Fig. 5.3) [4, 5]. 

Also the presence of a single resonance indieates a predominantly head-tail arrangement as in the case of the poly(carbophosphazene) (Fig. 5.10). 

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). 

Poly(heterophosphazene)s whose backbones comprise phosphoms, nitrogen, and another element - carbon or sulfur -were also synthesized. " In poly(carbophosphazene)s (poly-114), every third phosphoms atom is replaced by carbon. Poly-114 obtained in the thermal polymerization of a cyclic carbophosphazene was further transformed into white, solid, hydrolytically stable poly((aryloxy)carbophosphazene) (stmcture 115 Af -lO ). The polymer backbone in stmcture 115 was less flexible than in classical polyphosphazenes. The reaction of poly-114 with alkylamines was also studied. Poly (carbophosphazene) s have higher glass transition temperatures than their classical polyphosphazene counterparts with the same side groups. The increased stiffness of the carbophosphazene backbone is attributed to the high torsional barrier of the organic C = N n-bonds compared to the low barrier of the P = N n-bonds. ... 

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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