Polyisobutenes (or polyisobutylenes in American English) are amongst the first plastics ever synthesised intentionally by humankind. During the World Wars the need of natural rubber for automotive applications and war machines induced a shortage that ultimately boosted the development of new families of synthetic rubbers. For example, butyl rubber with unique gas barrier properties has become unreplaceable in the manufacture of tires. These materials have been further developed and specially engineered polyisobutenes are currently available for very specific applications. Polyisobutenes are present in our daily life passing most of the time unnoticed. For example, they are found in tires, sealing our food packages, in our double glazed windows, in chewing gum or in breast implants. The following work intends to provide in-depth knowledge on the family of polyisobutene rubbers, how to synthesize classical systems and how to approach the introduction of new functional groups in the polymer to expand the possible applications.