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

(hence

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

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

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

and

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

atoms, connected by alternating single and double

covalent bond A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

s. The compound can be prepared by polymerization of

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

((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 chemistry, inorganic-organic chemistry, organic polymers with a number of different polymer architecture, skeletal architectures with the backbone phosphorus, P-nitrogen, N-P-N-P-N-. In nea ...

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. Types of polyisoprene ...

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), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

.) In 1965, Harry R. Allcock at

Pennsylvania State University The Pennsylvania State University (Penn State or PSU) is a Public university, public Commonwealth System of Higher Education, state-related Land-grant university, land-grant research university with campuses and facilities throughout Pennsyl ...

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 and

benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

, 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 group is derived from a cy ...

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

) 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