| 초록 |
Phase behavior of asymmetric ABA triblock copolymer melts is studied within the Landau-Ginzburg model. By introducing a parameter t specifying the asymmetry around middle B-block, the Landau free energy is formulated in terms of t and minimized with respect to the parameters of mesophases (period, amplitude, type of mesophase). Using this weak segregation theory, the stability of mesophases such as hexagonal, body-centered cubic, double-gyroid, and lamellar ordered phases is investigated as a function of t. Furthermore, the theory is extended to an ABC triblock copolymer melt and the results such as spinodal instability are compared to the ABA triblock copolymer system. From the theory, we find non-linear t-dependence of the order-disorder transition (ODT) for both of ABA and ABC triblock copolymer system. The theory also provides an expression for the phase difference between the density fluctuations of two-ending A(C) blocks, which allow to investigate the detailed location of A(C) monomers in the ordered structure. |
