Poly(dichlorophosphazene), also called dichlorophosphazine polymer or phosphonitrilechloride polymer, is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with formula (PNCl₂)_''n''. It is an

inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...

(hence

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

-free) chloropolymer, whose backbone is a chain of alternating

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

and

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

atoms, connected by alternating single and double covalent bonds. The compound can be prepared by polymerization of

hexachlorophosphazene Hexachlorophosphazene is an inorganic compound with the formula . The molecule has a cyclic, unsaturated backbone consisting of alternating phosphorus and nitrogen centers, and can be viewed as a trimer of the hypothetical compound . Its classifi ...

((PNCl₂)₃) by heating to ca. 250 °C.Hans Rytger Kricheldorf (1991), ''Handbook of Polymer Synthesis''Mario Gleria, Roger De Jaeger (2004) ''Phosphazenes: A Worldwide Insight''Nova Publishers, 2004. 1047 pages. , 9781590334232 It is an "inorganic rubber" and the starting material for many other polymers with the -P=N- backbone (

polyphosphazene Polyphosphazenes include a wide range of hybrid inorganic-organic polymers with a number of different skeletal architectures with the backbone P- N-P-N-P-N-. In nearly all of these materials two organic side groups are attached to each phosphoru ...

s), which have important commercial uses.

History

Poly(dichlorophosphazene) was discovered by H. N. Stokes in the 19th century, and at that time its superior properties over

natural rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...

were already noted.H. N. Stokes (1895)
''On the chloronitrides of phosphorus''
American Chemical Journal, vol. 17, p. 275.H. N. Stokes (1896)
''On Trimetaphosphimic acid and its decomposition-products.''
American Chemical Journal, vol. 18 issue 8, p. 629. (The name "phosphimic" is used consistently in the title text. The work was done while the author was at the

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

.) In 1965, Harry R. Allcock at Pennsylvania State University synthesized a soluble form of the polymer, which opened the doors to the development of many derivatives.Mark, J. E.; Allcock, H. R.; West, R. “Inorganic Polymers” Prentice Hall, Englewood, NJ: 1992. .

Uses

Poly(dichlorophosphazene) is not water-resistant. However, it is soluble in organic solvents such as

THF Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...

and

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...

, wherein it can be derivatized by replacement of the chlorine atoms with -OR or -NR₂ groups (R =

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromaticity, aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar ...

) to yield many other polyphosphazenes. Some of these organically modified polymers are hydrolytically stable and exhibit some attractive properties such as low glass transition temperatures.

References

{{Reflist Inorganic polymers Phosphazenes Inorganic phosphorus compounds Inorganic chlorine compounds Inorganic nitrogen compounds