| 초록 |
A mean-field Landau analysis is performed to study surface ordering phenomena in A-b-B block copolymers that are compressible. The recently formulated Landau free energy for compressible diblock copolymers is applied to a symmetric diblock copolymer melt in the vicinity of a substrate or free surface following the concept of Fredrickson's work on incompressible copolymers. It was shown in our previous works on compressible block copolymers that an effective Flory-type interaction parameter χcRPA, which carries not only the change in contact interactions but also compressibility difference between blocks, was shown to play a central role in understanding the phase behavior of the copolymers in the bulk. It is required to properly modify χcRPA due to the presence of the surface. An field H describing a preferential affinity for one of two block components is additionally required here to understand the surface ordering phenomena. It is also of our interest to study the effects of hydrostatic pressure on the surface ordering behavior of the copolymers. A tentative variation of the modification of χcRPA and the field H will be attempted here to compute the changes in composition profiles and their pressure responses. |
