Butyl rubber

also known as isobutylene-isoprene rubber (IIR)

is a synthetic elastomer produced by cationic copolymerization of isobutylene with around 0.6 to 2.5 percent isoprene in chlorocarbon solvents at low temperature. Butyl rubber has unique elastomeric properties that makes it a good choice for a wide variety of rubber goods. Its excellent impermeability to gas diffusion together with its flexibility makes it the ideal material for inner tubes of tires and other highpressure tubes. The isoprene provides the necessary unsaturation sites for crosslinking. Thus

improving the degree of unsaturation (D

u

%) of butyl rubber can enhance the vulcanization efficiency

and the bonding property between the butyl rubber and other kinds of rubber is improved

which will broaden the application of butyl rubber. In this review

we provide an overview of the research progress of the synthesis and preparation of high unsaturated butyl rubber. Four kinds of initiators

for instance

Lewis acids and organic halides

coordination complex consisting of cationic source derived from metallocene or organometallics and weak coordinate anions

alkyl halides of aluminum and chlorides of zinc alkyls

are summarized and elaborated in this review. Moreover

we prospect the development of high unsaturated butyl rubber. This review will undoubtedly act as a great reference and theoretical guidance for researchers engaged in synthesizing and preparing high unsaturated butyl rubber.