Microphase separation in melts of double comb copolymers

Within the random-phase approximation, the conditions providing instability of a spatially homogeneous state of melts of double comb copolymers relative to microphase separation have been studied. As compared with the case of diblock copolymer melt connectivity between branch points of linear diblock copolymers and a backbone (densely grafted comb copolymer) is expected to assist the transition from the spatially homogeneous state to the microphase separated state; in other words, this factor decreases the incompatibility parameter at the transition point. Two characteristic types of spinodal behavior as a function of the number of repeating units have been found: one type is observed when the fragment of backbone between neighboring branch points is long; another type of behavior takes place when this distance is small. In one of the cases under study, the period of microstructure abruptly changes with variation of the interaction parameters of the system.