21.2 : 共重合体の特性と命名法

Copolymers are obtained by the polymerization of two or more different monomers together.

Consider the copolymerization of styrene and acrylonitrile monomers to make polystyrene-co-acrylonitrile. Here, the polymer name contains both monomer units, the infix  'co', and the prefix 'poly'.

Copolymers are usually represented by placing separate parentheses or brackets and degrees of polymerization around each type of repeating unit.*

Alternatively, a simplified expression places the parentheses around the bonded comonomers  with a common degree of polymerization.

If each monomer preferentially binds to the comonomer rather than the same type, the polymerization will result in an alternating copolymer. On the other hand, a lack of any preference between homo- and copolymerization leads to a random copolymer.

Blocks of homopolymers from a unique monomer can be synthesized by switching between polymerization conditions favorable for each monomer.

If the homopolymer blocks are alternating, it is a block copolymer.

If one homopolymer is grafted onto the other type of homopolymer chain, it is a graft copolymer.