ABSTRACT
Abinary (AB) polymermixture undergoesmacrophase separation at low temperatures if there is a short-range repulsive interaction between the A and B monomers. The kinetics of phase separation has been discussed extensively in Chapter 1 and subsequent chapters. Let us now consider a situation where the different polymer chains are connected by a covalent bond at the chain ends, as shown in Figure 7.1. In this case, macrophase separation is impossible-what happens instead is microphase separation, where A-rich and B-rich domains are arrayed in a lamellar structure with a typical spatial period of the order 50 nm, which is comparable with the size of each polymer chain [1]. (Lamellar ordering was briefly discussed
in Section 4.4.1.) If the ratio of the molecular weights of the A and B blocks is different, other morphologies appear such as gyroids, hexagonal structures of cylindrical domains, and body-centered-cubic (BCC) structures of spherical domains. These four fundamental structures are displayed in Figures 7.2 and 7.3.
