Weak-segregation theory of microphase separation in block copolymers - Part I

Block copolymers are polymers consisting of two or more chemically distinct blocks. Typically, the blocks are incompatible with each other which, below certain temperature, leads to the tendency of blocks separating in space. However, since the blocks are connected into chains, this tendency never results in large regions of space filled with only one block. Instead, one typically finds various spatially periodic arrangement of block with sizes being of order of ~100 nm -- a phenomenon known as microphase separation. In this talk I will go through the paper by Ludwik Leibler [Macromolecules v.13, 1602 (1980)] who was the first to describe theoretically weak microphase separation. We will derive a Landau-Ginzburg free energy for a diblock copolymer melt and relate its coefficients to the properties of a single chain. Phase diagram of a diblock copolymer melt will be discussed.