ELASTIC PROPERTIES OF HOMOPOLYMER-HOMOPOLYMER INTERFACES CONTAINING DIBLOCK COPOLYMERS

We study the elastic properties of homopolymer/hompolymer interfaces c ontaining diblock copolymers by means of a theory of Gaussian fluctuat ions, The interfacial tension and the bending rigidity of the interfac e in the two-phase coexistence region are calculated from the power sp ectrum of capillary modes, Our theory shows that in the limiting case of a pure binary homopolymer mixture, while the interfacial tension in creases monotonically with increasing chi N (where chi is the Flory-Hu ggins parameter and N is the homopolymer molecular weight) the bending rigidity does not. The bending rigidity increases rapidly at first fo r small values of chi N, but then decreases with further increase of c hi N. In the presence of diblock copolymers, the interfacial tension a lways decreases with increasing diblock copolymer volume fraction at a given chi N. However, the bending rigidity can show either a decrease or an increase depending on chi N and the ratio gamma between the mol ecular weights of a diblock copolymer and that of a homopolymer. Our r esults for the surface pressure and the bending rigidity are further c ompared with results based on scaling arguments of wet polymer brushes . (C) 1998 American Institute of Physics.