“Recognition” of copolymers and stereoisomers in macromolecule complexation reactions in dilute solutions

Theoretical relationships have been obtained describing the dependence of selectivity (or molecular “recognition”) on the length of reacting polymer chains in reactions between complementary macromolecules. The possibility of highly efficient separation of mixtures of macromolecules, differing little in chemical structure, was predicted as well as of fractionation of compositionally inhomogeneous copolymers by means of polymer-polymer interactions. Experimentally it has been found that polyethylene glycol mixed with polymethacrylic acid stereoisomers is selectively bound in a polycomplex with macromolecules enriched with iso-triads; polyvinylpyrrolidone is selectively bound to those poor in iso-triads. Polyvinylpyrrolidone selectively binds polymethacrylic acid in mixtures with copolymers of acrylic and methacrylic acids. The degree of “recognition” of a macromolecule of given chemical structure by an oligomer increases with increasing oligomer chain length and is in a quantitative agreement with the theoretical equation. It has been shown that, in aqueous solution for interaction of polyacrylic acid with compositionally inhomogeneous copolymer of 4-vinylpyridine and N-ethyl-4-vinylpyridinium bromide (partially quaternized polyvinylpyridine), the polyacrylic acid binds selectively the fractions rich in non-alkylated units. This result can be explained quantitatively in terms of the theory.