Polyisoprene is strictly speaking a collective name for

polymers A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...

that are produced by

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are ...

isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals ...

. In practice polyisoprene is commonly used to refer to synthetic ''cis''-1,4-polyisoprene, made by the industrial polymerisation of isoprene. Natural forms of polyisoprene are also used in substantial quantities, the most important being 'natural rubber' (mostly ''cis''-1,4-polyisoprene), which is derived from the sap of trees. Both synthetic polyisoprene and natural rubber are highly elastic and consequently used to make tires and a variety of other applications. The ''trans'' isomer, which is much harder than the ''cis'' isomer, has also seen significant use in the past. It too has been synthesised and extracted from plant sap, the latter resin being known as

gutta-percha Gutta-percha is a tree of the genus ''Palaquium'' in the family Sapotaceae. The name also refers to the rigid, naturally biologically inert, resilient, electrically nonconductive, thermoplastic latex derived from the tree, particularly from ' ...

. These were widely used as an electrical insulator and as components of

golf ball A golf ball is a special ball designed to be used in the game of golf. Under the rules of golf, a golf ball has a mass no more than , has a diameter not less than , and performs within specified velocity, distance, and symmetry limits. Like g ...

s. Annual worldwide production of synthetic polyisoprene was 13 million tons in 2007 and 16 million tons in 2020.

Synthesis

In principle, the polymerization of isoprene can result in four different

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

. The relative amount of each isomer in the polymer is dependent on the

mechanism Mechanism may refer to: * Mechanism (engineering), rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission *Mechanism (biology), explaining how a feature is created *Mechanism (philosophy), a theory that ...

of the polymerization reaction. Anionic chain polymerization, which is initiated by ''n''-Butyllithium, produces ''cis''-1,4-polyisoprene dominant polyisoprene. 90–92% of repeating units are ''cis''-1,4-, 2–3% ''trans''-1,4- and 6–7% 3,4-units.Jürgen Falbe, Manfred Regitz (Hrsg.): ''CD Römpp Chemie Lexikon'', Thieme, Stuttgart, 1995. Coordinative chain polymerization: With

Ziegler–Natta catalyst A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes (alpha-olefins). Two broad classes of Ziegler–Natta catalysts are employed, distinguished by their solubility: * He ...

TiCl₄/Al(''i''-C₄H₉)₃, a more pure ''cis''-1,4-polyisoprene similar to natural rubber is formed. With Ziegler–Natta catalyst VCl₃/Al(''i''-C₄H₉)₃, ''trans''-dominant polyisoprene is formed.Bernd Tieke, ''Makromolekulare Chemie'', 3. Auflage, Wiley-VCH, Weinheim, 2014, S. 149. 1,2 and 3,4 dominant polyisoprene is produced MoO₂Cl₂ catalyst supported by phosphorus ligand and Al(OPhCH₃)(''i''-Bu)₂ co-catalyst.

History

The first reported commercialisation of a stereoregular poly-1,4-isoprene with > 90% cis (90% to 92%) was in 1960 by the Shell Chemical Company. Shell used an alkyl lithium catalyst. 90% cis-1,4 content proved insufficiently crystalline to be useful. In In 1962, Goodyear succeeded in making a 98.5% cis polymer using a Ziegler-Natta catalyst, and this went on to commercial success. Significant producers include: * Nizhnekamskneftekhim * JSR Corporation * Karbochem *

Kuraray is a Japanese manufacturer of chemicals, fibers and other materials. Their main manufacturing facilities are located in Kurashiki, Okayama. The company's Tokyo administrative offices are located in Otemachi, Chiyoda in the Ote Center Building ...

* SK Premyer * Volzhski Kauchuk * Togliattisyntezkauchuk * Goodyear *

Zeon , also known as ''First Gundam'', ''Gundam 0079'' or simply ''Gundam '79'', is an anime television series, produced and animated by Nippon Sunrise. Created and directed by Yoshiyuki Tomino, it premiered in Japan on Nagoya Broadcasting ...

* Braskem (Brazil) * LyondellBasell * SIBUR (Russia) * Chevron Phillips Chemical Company * China Petrochemical Corporation (China), * Dow (US), * Pon Pure Chemicals (India), * Zibo Luhua Hongjin New Material Co, * Exxon Mobil Corporation

Usage

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 ...

and synthetic polyisoprene are used primarily for

tires A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...

. Other applications include latex products, footwear, belting and hoses and

condoms A condom is a sheath-shaped barrier device used during sexual intercourse to reduce the probability of pregnancy or a sexually transmitted infection (STI). There are both male and female condoms. With proper use—and use at every act of inte ...

. Natural

and synthetic ''trans''-1,4-polyisoprene were used for

References

{{reflist Rubber Organic polymers

Synthesis

History

Usage

See also

References