Similarity phosphazene

Poly(phosphazenes) are similar, partly inorganic polymers in that they consist of inorganic backbone, in this case of nitrogen and phosphorus atoms. They are separated formally by alternating single and double bonds and carry organic groups on the phosphorus atoms (10.3). 

The first phenomenon observed is the improved resistance of these materials to combustion, in a way that they may be classified as intrinsically self-extinguishing substrates. For instance, the LOI value for PTFEP is reported to be 48 [452], which is much higher than reported for classical organic plastics [283], while phosphazene fluoroelastomers have been considered as fire-retardant materials since the very beginning of their preparation and utilization [562]. Similarly to aryloxy- and arylamino- substituted POPs [389,390] (vide infra),it may be expected that the flame-resistance properties of phosphazene fluoroelastomers could be successively exported to stabihze organic macromolecules when blended with these materials. 

Similarly to PTFEP, phosphazene fluoroelastomers proved to be rather stable to thermal treatments up to 175 °C [560,561], while for temperatures above this value degradation phenomena start to be relevant. 

Upon applying the calibration constants obtained from the data of one sample to evaluate the SEC data of the other samples, the calculated Mn and values correspond fairly well (within 10-20%) with the absolute MW parameters of the samples. This agreement also suggests that the samples probably have similar chain structures. The distribution functions for samples PN-1 and IL-22 are plotted in Figures 4 and 5. The molecular weight distributions of both polymers are similar to distribution curves reported for derivatized poly(organo)phosphazenes (4-10). 

This chapter covers the literatures of phosph(v)azenes. The general pattern of development in this area is similar to that observed in previous yearly reviews with additional interest being shown in polyphosphazenes and in a variety of molecular orbital calculations of both linear and cyclic phosphazenes. 

Second, dopamine has been linked covalently to a poly(aryloxy-phosphazene) via a diazo-coupling technique (24). Experiments showed that rat pituitary cells in culture responded to the surface-bound dopamine in a similar manner to that found when the dopamine was free in solution. 

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.)... 

This result has been further substantiated by the work of Koppel et al. <2001PCA9575>. They conducted a theoretical study of the basicity of phosphorus imines and ylides. Verkade bases 6-8 were included. They showed basicities comparable to commercially used organic superbases (/-BUP4 phosphazene imine), with compound 8 in particular giving calculated basicities similar to Li3P and Li20. 

Similar treatment of 5-nitrobenzothiadiazole 97 with ethyl isocyanoacetate and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) gave the thiadiazolo[3,4-< ]isoindole 93 (21%), but when a phosphazene base was employed the major isolated product was the pyrimidine fV-oxide 98 (46%) (Equation 13) <1996J(P1)1403, 1996TL8391>. 

Here it is sufficient to note that several hundred poly(organo-phosphazenes) have been prepared by this method. Polymers of this type are already being used in technology they are also of considerable scientific Interest. Similar syntheses have been developed based on poly(difluorophosphazene), (NPF2) ( ). ... 

Poly(phosphazene) microparticles have shown the potential for oral protein or peptide delivery (Vandorpe et al. 1996 Veronese et al. 1998 Passi et al. 2000). The processing of these materials is very similar to poly(esters) and the biocompatibility of the polymers is exceptional. After the implantation of matrices of poly(phosp-hazene), no gross areas of inflammation were observed at explanation (Laurencin et al. 1987). The only negative aspect of these materials is that FDA approval of this polymer class has little precedent. 

The system aminophosphorane (116)-phosphazene (116a) (Scheme 29) studied by Sanchez et al,191 was found to behave differently only 116a can be detected by NMR, i.e. there is no equilibrium. Exactly the opposite situation was found with the system 117-118, in which the only observable species was the aminophosphorane 117. Evidently, the increase in thermodynamic stability results from the formation of a spirophosphorane structure. Similar conclusions were reached by Gololobov et al.191 in the course of a study of structures similar to that of 117. More recently, Stegmann et al.193 extended the scope of their research to substituted 1,2-aryldiamines in a study of the equilibria 119 119a and 120 120a. The thermodynamic parameters AH, AG and AS were determined by NMR. Here too, the position of the equilibrium was found to depend on the substituents (steric and electronic effects), on the solvent and on the temperature. 

The amides of phosphorus can be similarly obtained, using either PC13, POCl3 or PC1S, for example.24 27 However, with PC15 only secondary amines yield amides,27 primary amines generally giving phosphazene derivatives.28... 

Similar trends are observed for the metal complexes prepared in the present study. The mode of coordination of cyclophosphazenes to transition metal ions mainly depends upon the ring size and the nature of the substituent. The rigid six-membered cyclotri-phosphazenes have low propensity for forming metal complexes and clearly steric effects predominate. 

Compounds with an endocyclic N = P bond (alkyl-, arylphosphazenes) behave similarly, forming complexes of structure 399 with a P-coordinated ligand [112]. Information on other phosphazene complexes can be found elsewhere [700]. 

A novel reaction of quaternary AT-methylphosphazenium iodides, [N P Me2n+i] Ie(n = 3, 4), with sodium bis(trimethylsilyl)amide has been reported. Phosphorines with exocyclic methylamino groups are formed as a result of phosphazene ring cleavage. Similar cleavage occurs in the reaction of quaternary phosphazenium iodides with potassium-i-butoxide (97). 

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