Polyphosphazenes, effect properties

Anurima S, Nicholas RK, Swaminathan S, Lakshmi SN, Jacqueline LS, Paul WB, Cato TL, and Harry RA. Effect of side group chemistry on the properties of biodegradable L-alanine cosubstituted polyphosphazenes. Biomacromolecules, 2006, 7, 914-918. 

JThe effect of the substituent on the properties of the polyphosphazenes is not fully understood. For instance, [NP(OCH ) ]n and [NP C CH. homopolymers are elastomers (8,29). Synthesis using lithium, in contrast to sodium, salts is claimed to produce rubber-like fluoroalkoxyphosphazene polymers (30). The presence of unreacted chlorine or low molecular weight oligomers can affect the bulk properties (31,32). Studies with phosphazene copolymers both in solution and in the bulk state (29,33-38) indicate a rather complex structure, which points out the need for additional work on the chain structure and morphology of these polymers. 

Enough is now known about the effect of different side groups attached to a polyphosphazene chain to allow some general structure-property relationships to be understood. To a limited extent, these relationships allow the prediction of the properties of polymers not yet synthesized. Some general relationships will be described in the following sections, but specific properties associated with certain side groups are summarized in Table 3.1. 

As a coating offers increased anti-icing effectiveness and durability than fluorocarbon and silicone elastomers. These icephobic coats can reduce the accumulation of ice on products such as rooftops, aircraft, radomes, antennas, ships, and power-transmission lines. The weight of such accumulations of ice has led to aircraft crashes, fallen power lines, etc. The icephobic coats reduce the adhesive force between ice and a surface. Polyphosphazene elastomers possess these desired properties, in addition have low glass transition temperature (Tg), good environmental stability, curability, and moderate cost. 

Now that polymerization control has been established, these techniques may lead to cost-effective and new developments/ applications in this interesting class of polymers. Some physical properties that are sensitive to structure and chain conformations may require further investigation. Some of these polyphosphazenes are to be found among the polymers that follow. 

With the rapid expansion in controlled radical polymerisation chemistry, for example, atom-transfer radical-polymerisation (ATRP) [47], it is clear that combinations with the inorganic polyphosphazene backbone, and its many unique properties, can add extra dimensions and multiply the opportunity for new hybrid materials. As the inorganic component in such polymers is low, often below 5%, the resultant polymers often possess the solution, chemical and biological properties of the attached organic component and can, in effect, be viewed as highly branched versions on an inorganic (potentially degradable) backbone. 

It is a prerequisite that after implantation of the newly established tissue into an organism the scaffold, as a foreign material, should show clear effects of bioerosion and bioresorption under the influence of cells after a short period. A few polymers exhibit this behaviour, such as polyesters like poly(lactic acid) (PLA), poly(glycolic acid) or their copolymers poly(lactic-co-glycolic acid) (PLGA). Polyphosphazenes are known to be converted into harmless phosphates and ammonia salts and, together with residues of carbon-based side arms, should be excreted easily from the body. Furthermore, polyphosphazenes and their properties can be tailored, leading to defined bioresorption kinetics, defined pore sizes and defined additional chemical functionalities. Thus, polyphosphazenes can be considered as extraordinary materials for the synthesis of scaffolds to be applied in TE. 

Bose, S., Pramanik, N., Das, C.K., Ranjan, A., and Saxena, A.K. (2010) Synthesis and effect of polyphosphazenes on the thermal, mechanical and morphological properties of poly(etherimide)/ thermotropic liquid crystalline polymer blend. Mater. Des., 31,1148-1155. 

It is generally agreed that the physical property differences between organic-type pol3nners can be attributed to differences in crystallinity, to side group steric or polar effects, and occasionally to the existence of cis-trans isomerism about double bonds in the skeleton. To what extent are the properties of polyphosphazenes determined by the same factors ... 

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