Polyphosphazenes containing

In conclusion, polyphosphazenes containing fluoroalkoxy groups as side phosphorus substituents constitute one of the most relevant class of macromolecules of this family and have attracted remarkable interest in the past because of their outstanding properties and wide range of applicability, especially in low and high temperature domains, and have received renewed interest in more recent times [399,457]. 

This effect has also been observed in polyphosphazenes containing alkyl- or phenyl-carborane as pendent groups.12 A typical synthetic route to poly(phenyl-carboranyl-di-trifluoroethoxy-phosphazene) having pendent phenyl-carborane groups is shown in scheme 4. A substantial improvement in the thermal stability of the polymer was observed. This is attributed to a retardation of the ring-chain de-polymerization mechanism due to steric hindrance effects of the carborane units, inhibiting helical coil formation. 

The study by Percec, Tomazos and Willingham (15) looked at the influence of polymer backbone flexibility on the phase transition temperatures of side chain liquid crystalline polymethacrylate, polyacrylate, polymethylsiloxane and polyphosphazene containing a stilbene side chain. Upon cooling from the isotropic state, golymer IV displays a monotropic nematic mesophase between 106 and 64 C. In this study, the polymers with the more rigid backbones displayed enantiotropic liquid crystalline behavior, whereas the polymers with the flexible backbones, including the siloxane and the polyphosphazene, displayed monotropic nematic mesophases. The examples in this study demonstrated how kinetically controlled side chain crystallization influences the thermodynamically controlled mesomorphic phase through the flexibility of the polymer backbone. 

Zumbulyadis et al. [86] selected a fluorinated polyphosphazene, containing CF3CF2CF2CF2CH2O side chains (attached to phosphorus atoms in the polymer backbone) to explore the potential of F MAS/NOESY experiments. MAS at 3.82 kHz sufficed to resolve all four F sites, though effects of isotropic indirect coupling were obscured by the linewidths. Cross peaks are seen in the two-dimensional NOESY spectrum. The authors argue that these arise from NOE processes and not from spin diffusion. 

Polyphosphazenes containing nitrogen and phosphorus have been synthesized by replacing the chlorine atoms on the backbone chain of polymeric phosphonitrilic chloride (dichlorophosphazene) by alkoxy or fluoroalkoxy groups. These derivative polymers do not exhibit the hydrolytic instability of the parent polymer. The general synthesis scheme is... 

L.Y. Qiu, K.J. Zhu, Novel biodegradable polyphosphazenes containing glycine ethyl ester and benzyl ester of amino acethydroxamic acid as cosubstituents, J. Appl. Polym. Sci. 77 (13) (2000) 2987-2995. 

Qiu, L. Y. Yan, M. Q. (2009) Constmcting doxombicin-loaded pol3nneric micelles through amphiphihc graft polyphosphazenes containing ethyl tryptophan and PEG segments. Acta Biomater, 5, 2132-41. 

Polyphosphazenes containing CFj CH2- and HCF2(CF2) CH2-0- gronps retain their flexibility over large temperatnre ranges and as such have found application in braking systems of high-performance aircraft [80],... 

Thionylphosphazene polymers can be obtained by condensation of linear compounds (112.252) [99]. Products include gums, glasses and elastomers. Polyphosphazenes containing carbon atoms in the main chain have also been made (12.253) [100,101]. 

The second limitation of the macromolecular substitution reaction is that it cannot be applied for the preparation of polyphosphazenes containing P-C bonds. 

Preparation of Polyphosphazenes Containing P-C Bonds by Thermal Treatment of Phosphoranimines... 

Polyphosphazenes containing phosphino ligands can be prepared as shown in Fig. 3.43. 

Polyphosphazenes can be modified to incorporate new functional groups. Thus, for example polyphosphazenes containing carboxy groups can be obtained by the methodology shown in Fig. 3.44. 

Complex polyphosphazenes containing giucosyi side-groups have been prepared (Figs. 3.46-3.47) [35]. The multifunctional nature of the glucose reagents implies that some of these reactive groups have to be protected... 

The phosphorus NMR chemical shifts of a few selected polyphosphazenes are given in Table 3.7. Usually slightly broad signals are seen in the NMR spectrum of the polymers because of the inerease in viscosity when polymers are dissolved in solution. The P-NMR chemical shifts of polyphosphazenes indicate that these are about 20-30 ppm upfield shifted with respect to the cyclic trimers. The cyclic tetramers have intermediate chemical shifts (entries 1, 2, 5, 8, 11 in Table 3.7). In polyphosphazenes containing mixed substituents the P-NMR chemical shifts are diagnostic... 

Fig. 3.55. Polyphosphazenes containing amino acid ester side-groups...

Fig. 3.56. Synthesis of polyphosphazenes containing NLO-imparting organic side-groups...

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]. 

Biodegradable polyphosphazenes containing steroidal and amino acid ester groups have been prepared by Allcock et al. (1980) (Figure 20). 

Biodegradable polyphosphazenes containing esters of glycolic or lactic acid as side groups (Allcock et al, 1994) have been described (ffi ucee2 . The degradation... 

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