Ordering at two length scales in comb-coil diblock copolymers consisting of only two different monomers

The microphase-separated morphology of a melt of a specific class of comb-coil diblock copolymers, consisting of an AB comb block and a linear homopolymer A block, is analyzed in the weak segregation limit. On increasing the length of the homopolymer A block, the systems go through a characteristic series of structural transitions. Starting from the pure comb copolymer, the first series of structures involve a short length scale followed by structures involving a large length scale. A maximum of two critical points exists. Furthermore, in the two parameter space characterizing the comb-coil diblock copolymer molecules considered, a nontrivial bifurcation point exists beyond which the structure factor can have two maxima (two correlation hole peaks).