Blocks coplymers - Thermoplastic polymers, elastomers and additives

Most thermoplastic elastomers are block or graft copolymers. The terminology applied usually uses A to represent a type of units and B and C in a similar way. Thus, AB represents a di-block copolymer, ABC a tri-block in which all the segments have polymerized from different monomers, and ABA two terminal blocks A and a central block B. It is also common to use the English initial of the monomer to represent the copolymer; thus S and B correspond to styrene and butadiene in S-B-S.

The polymerization of these materials occurs in two ways: anionic polymerization and organ-metal catalysis, basically with lithium alkyls. These complex polymers generally have an unusual characteristic: they have two differentiated Tg due to their segmented composition of two types of polymer, one of which establishes crosslinking points and the other presents an elastic linear chain.