Lattice cluster theory for pedestrian. 2. Random copolymer systems

An analytically tractable, more realistic extension of random copolymer Flo ry-Huggins (FH) theory Is developed for A(x)B(1-x)/CyD1-y, A(x)B(1-x)/A(y)B (1-y), and A/CyD1-y random copolymer binary blends. The theory describes th e polymer-polymer interactions in terms of the interactions between united atom groups and includes a temperature-independent contribution chi(s) to t he effective interaction parameter chi. chi(s) is determined (with no adjus table parameters) from the lattice cluster theory in the incompressible, at hermal, fully flexible, long-chain limit. The general, readily applied expr essions for the interaction parameter chi are illustrated for norbornene-co -ethylene (NxE1-x/NyE1-y) random copolymer mixtures for which the theory ha s been successfully used by Delfolie et al. (Macromolecules 1999, 32, 7781) to explain miscibility data that depart significantly from the predictions of classic random copolymer FH theory. Further illustrations describe the influence of chain semiflexibility and sequence dependence on the miscibili ty of NxE1-x/NyE1-y blends. The theory is then applied to isotopic mixtures of saturated poly(butadienes) (sPB) whose randomness stems from the random addition of 1,2 and 1,4 units in the polymerization process. A final appli cation treats blends of ethylene-co-alpha-alkene random copolymers with sPB .