Microphase separation in multiblock copolymer melts:Nonconventional morphologies and two-length-scale switching

The phase behavior of A(fmN)(B(N/2)A(N/2))B(1-f)mN multiblock copolymer melts is studied within the weak segregation theory. The interplay between ordering on different length scales is shown to cause dramatic changes both in the ordered phase symmetry and periodicity upon small variation of the architectural parameters of the macromolecules. Phase diagrams are presented in the (f,chi N) plane (chi is the Flory-Huggins parameter) for various values of the architecture parameters n and m. Near the critical surface, i.e., for (f-0.5)(2)