A study of the structure and properties of three block copolymers in solution by the 'computer experiment' method

The structure of macromolecules of a three block copolymer of the type ABA in selective solvents is discussed. Structural characteristics of copolymers with the Gaussian approximation and for flexible lattice chains have been calculated by computer modelling. It is shown that symmetrical three block copolymers have a dumb-bell structure which is retained over a wide range of selective solvents, from good solvents for the different blocks up to conditions corresponding to non-solvents. An increase in the molecular mass of the polymer chain, the ratio between the lengths of the middle and end blocks being constant, thus stabilizes the dumb-bell structure. It is shown that, although the overall dimensions of the chain are considerably decreased on going from good solvents for the end blocks to θ conditions (or a non-solvent), the dimensions of the middle block change only slightly and the links located in the end blocks touch only to a small extent. The intermolecular structures formed in solutions of two and three block copolymers are discussed.