TABLE OF CONTENTS Block copolymers consist of chemically distinct polymer chains that are tethered together to form a single macromolecule. If the individual blocks are immiscible when they are unattached, phase separation will also normally occur in the case of the copolymer, with morphologies that depend on the relative composition of the separate block species, and their manner of attachment (diblocks, triblocks, stars, etc.). This is a result of the physical connection of the blocks, which prevents them from separating over distances greater than the contour lengths of the respective blocks. The result is a microphase separation with adjacent domains that are richer in either of the chemical species.
As the blocks attempt to phase separate and reduce the enthalpic penalty that drives immiscibility, their connectivity also imposes conformation restrictions that will oppose large elongations of the chains because of entropic considerations. As a consequence of these two competing mechanisms, microphase domains tend to be on the order of the radius of gyration of the blocks. The transition from an amorphous state to a microphase separated state identifies the microphase separation temperature (MST). Above this temperature, Gaussian statistics are expected to apply to the chains of each block. Below this temperature, where strong segregation occurs, the interface between domains will sharpen. Furthermore, the constraint of incompressibility requires uniform space filling of the polymer segments and the available chain conformations become restricted. When this occurs, a departure from Gaussian statistics may occur, and this can...
