Self-assembled structures in polystyrene-block- polyisoprene-blend-polystyrene and polystyrene-block-poly(methyl methacrylate)-blend-polystyrene or -blend-poly(methyl methacrylate) in the strong segregation regime

This study deals with the investigation of microphase-separated morphology and phase behaviour in blends of polystyrene-block-polyisoprene with homopolystyrene and blends of polystyrene-block-poly(methyl methacrylate) with homopoly(methyl methacrylate) or homopolystyrene in the strong segregation regime using small-angle X-ray scattering and transmission electron microscopy as a function of composition, molecular weight of homopolymers, r(M) and temperature. Parameter r(M) = M(H)/M(C) (where M(H) is the molecular weight of homopolymer and M(C) that of the corresponding block copolymer) was selected to encompass behaviour of the chains denoted as a 'wet brush' (i.e. r(M) < 1). The relative domain spacing D/D(o) increases in the regime 0 < r(M) = 1 with increasing concentration of homopolymer w(P) and increasing r(M) but depends on the specific implemented morphology. We tested a new approximate D/D(o) versus W(P) relation in the strong segregation regime using block copolymers of high molecular weights. It is shown that the parameters r(M) and chi(3/2)N determine the slope of the D/D(o) versus w(P) relation in the strong segregation regime and the new approximation generally matches the experimental data better than the approximations used so far. (C) 2010 Society of Chemical Industry