polyisobutene

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|ImageFile = Polyisobutylene.svg

|ImageSize = 150px

|ImageFile1 = Oppanol b100.png

|ImageCaption1 = Sample of polyisobutene with a molecular weight of ~1,000,000[https://automotive-transportation.basf.com/global/en/fuel-and-lubricants/fuel-and-lubricant-solutions/polyisobutenes--pib-/oppanol_more-than-just-polyisobutene.html OPPANOL B 100 by BASF]

|OtherNames = Polyisobutylene; Poly(isobutene); Poly(isobutylene); PIB

|Section1 = {{Chembox Identifiers

|CASNo = 9003-27-4

|CASNo_Ref = {{cascite|correct|CAS}}

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = 241BN7J12Y

|ChEBI = 53725

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|Section2 = {{Chembox Properties

|Formula = (C₄H₈)_n

|MolarMass = Variable

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Polyisobutene (polyisobutylene) is a class of organic polymers prepared by polymerization of isobutene. The polymers often have the formula Me₃C[CH₂CMe₂]_nH (Me = CH₃). They are typically colorless gummy solids.

Cationic polymerization, initiated with a strong Brønsted or Lewis acid, is the typical method for its production. The molecular weight (MW) of the resulting polymer determines the applications. Low MW polyisobutene, a mixture of oligomers with M_ns of about 500, is used as plasticizers. Medium and high MW polyisobutenes, with M_n ≥ 20,000, are components of commercial adhesives.{{cite encyclopedia |author1=Kenneth S. Whiteley |author2=T. Geoffrey Heggs |author3=Hartmut Koch |author4=Ralph L. Mawer |author5=Wolfgang Immel |title=Polyolefins |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |year=2005 |publisher=Wiley-VCH |place=Weinheim |doi=10.1002/14356007.a21_487}}