The liquid rubbers are unsaturated homopolymers or copolymers having molecular weight below around 50,000, but the most common range of molecular weight is 1,000 to 10, 000. Eventhough liquid rubbers can be provided by a variety of polymerization methods involving free radical, cationic and coordination catalyst, anionic polymerization is one of the unique ways for the preparation of liquid rubbers because a variety of macrostructures and microstructures can be prepared by controlling the polymerization conditions.

In-chain and chain-end functionalizations of the liquid rubbers can be achieved by using the properly protected functional agents, functionalized initiators or terminators. Because of a higher level of unsaturation of liquid rubbers, post polymerization modification of liquid rubber can provide functional groups randomly distributed along the polymer backbone chain or saturation for better oxidation stability. Unfunctionalized liquid rubbers can be used for coatings, plasticizer and coagent, and functionalized liquid rubbers can be used for adhesion promoter, dispersing aids and co-monomers of copolymers like polyurethane.