Poly phosphazene Degradation

The degradation of the poly(phosphazenes) is very well understood, with the production of ethanol, phosphate, ammonium salts, and the pendant groups (Andrianov and Payne 1998). When the pendant group is an amino acid, all of the degradation... 

Diffusion of solutions of Cr, Co and Mn ions through a PTFE membrane allows for separation of Cr from the remaining ions. Thermal stability of polymeric materials is a significant consideration in many poly(phosphazene) applications. The kinetics of the thermal degradation of PTFE are best fit with a model requiring a two step initiation for depolymerization. These steps involve formation of defect units, such as =P(0)NH- and =P(0)N(CH2CFj)-, which become active centers for depolymerization. Mixed... 

Amino, alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

In vitro evaluations have been made. Bioerodible poly(phosphazenes) have the advantage that the degradation products are biocompatible. The majority of bioerodible poly(phosphazenes) have been synthesized by the classical thermal procedure of Allcock et al. (1965)—reference (15). The copolymer in question is described. In vivo performances in clinically relevant conditions are planned for PPHOS matrices. 

Studies by Pintauro and co-workers have shown that poly [(3-methylphenoxy) (phenoxy) phosphazene] and poly [bis (3-methylphenoxy) phosphazene] (Figure 37) can be sulfonated by adding an SO3 solution in dichloroethane dropwise to a polymer/dichloroethane solution.A high ion exchange capacity (up to 2.0 mequiv/g) material was reported with no detectable polymer degradation. 

Crommen, J.H.L., Schacht, E.H., and Mense, E.H.G. (1992). Biodegradable Polymers. 2. Degradation Characteristics of Hydrolysis-Sensitive Poly[(Qrgano)Phosphazenes]. Biomaterials, 13, 601-611. 

Tanigami, T., Ohta, H., Qrii, R., Yamaura, K., and Matsuzawa, S. (1995). Degradation of poly[bis(ethylamino)phosphazene] in aqueous- solution. J. Inorganic Organometallic Polymers, 5, 135-153. 

According to a similar mechanism, the photolysis of poly[bis(4-benzo-ylphenoxy)phosphazene] [poly(BPP)] in air equilibrated CH2CI2 solution induces chain scission and extensive degradation of the macromolecules [14],... 

Poly[bis(4-isopropylphenoxy)phosphazene] undergoes photosensitised degradation in solution in the presence of... 

Allcock studied the thermal degradation of poly [bis (trifluoroethoxy )-phosphazene] via gel permeation chromatography and solution viscosity measurements on samples aged at 150°-300°C (II) in sealed, evacuated tubes. The mechanism of degradation was presented as a two-step process (1) chain scission at weak links and (2) depolymerization to cyclic oligomers. Allcock also reported similar studies on the thermal breakdown of poly [bis (phenoxy) phosphazene] and arrived at the same degradation mechanism (12). 

Thermal degradation poly(tri-fluoroethoxy-phosphazene) (homopolymers)... 

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