The molecular weights of the blocks and the overall composition of the block copolymer cannot be varied independently. Therefore, a classical phase diagram, such as shown in Figure 1, cannot exist, The result has been a plethora of new notation. In Figure 2, c Z represents the heat of mixing per chain. An UCOT implies a nucleation and growth mechanism for the kinetics of phase separation. Whether one speaks of a LCST and an UCST or a LCOT and an UCOT, it must be noted that the UCST and UCOT appear at lower temperatures than the corresponding LCST and LCOT, respectively.
Most block copolymers are phase separated, that is, the two kinds of blocks are immiscible.
The three most common morphologies observed are spheres, cylinders, and lamellae. A major restriction on all block copolymer morphologies is that the interfaces must be placed relative to one another such that the junction between the blocks can fit easily. There are several other possible morphologies that fit this restriction, the subject of future research. Overall, the whole area of block copolymer phase separation and morphology lacks a coherent and accepted nomenclature, although its great importance is leading to continuous and numerous research programs. Ed., Blackwell Scientific Publications, Oxford, 1991.