Analyze the widespread use of polyphosphazenes in various fields of science. Describe the methods of synthesis of polyphosphazenes.

POLYPHOSPHASENES (polyphosphonitriles), polymers, phosphazogroupcontentDivided into homopolyphosphazenes [- (R) 2P = N—] n, heteropolyphosphazenes [—N = P (R2) —X—] “and polyphosphazenes containing phosphazogroups in the side chain (in -lah R = C1, org. or element-org. radical; X-org. residue). The most value in scientific and practical. respect have homopolyphosphazene.

The synthesis of most types of polyphosphazenesis based on the use of chlorophosphazenes obtained by partial ammonolysis of PC15:

Basics the component in the mixture of the homologs formed is cyclic. trimer (hexachlorocyclophosphazene; n = 3). Above 200 ° C, it is polymerized with a ring opening and the formation of vysokol. inorganic rubber - polydichlorophosphazene (polyphosphonitrile):

The latter is rapidly hydrolyzed in air. However, due to the high chemical. activity chlorine atoms can be replaced by decomp. org. radicals (for example, OR, NHR, SR, alkyl) by treatment of polydichlorophosphazene with alcohols, alcohols, phenolates, amines, metalloorg. compounds. The resulting polyorganophosphazenes are in most cases chemically inert, sol. in org. p-ritels. Depending on the nature of the side radicals, you may have either plastics or rubbers. Many polyphosphazene can be in the liquid crystal. condition in which they pass from crystalline. states at t-pe T1 (see table). Polyorganophosphazenesare used to obtain elastomers that are used at low temperatures and in aggressive environments. In practice, copolymer perfluoroalkoxyphosphazenesare more commonly used for these purposes. After the introduction of 30-40% by weight of filler (Aerosil, clay or A12O3), a stabilizer and afterbirth. vulcanization get non-brittle at t-rah below - 100 ° C materials having a modulus of elasticity at 100% elongation of 3.5-10.5 MPa, age of 7-14 MPa, relates. elongation of 100-200%; they are resistant to fuels, oils and hydraulics. liquids. They are made of flange seals, sealing and damping pads, cuffs and hoses for fuel in the aviation and other industries.

Homopolyphosphazenes are also used in the production of non-combustible polymeric materials (polyphosphazenes themselves self-extinguish or do not burn, their oxygen index is> 25), in medicine, to create thromboresistant materials [poly-bis (tri-fluoroethoxy) phosphazene], as adjustable implants the rate of resorption (polyorganoaminophosphazenes containing organooxy and organoamino groups on the P atom) and for the preparation of prolonged medicinal sr-in.

Heteropolyphosphazene obtained by polycondensation of chlorophosphazenes with polyfunctional. phenols and amines (polyphosphazenes based on diatomic phenols are most important). They are phosphorus-containing analogs of phenolic and amino-dehydric resins. Such polyphosphazenesare used as binders for plastics with enhanced flame and heat resistance, as film formers for paints and varnishes and adhesives.