Microphase-Separated Morphology and Liquid Crystal Orientation in Block Copolymers Comprising a Main-Chain Liquid Crystalline Central Segment Connected to Side-Chain Liquid Crystalline Segments at Both Ends

The self-assembly behavior of ABA triblock copolymers comprising side-chain (SC) liquid crystalline (LC) polymer (A blocks) and a main-chain (MC) LC polyester (B block) is investigated for SCLC segment volume fractions (phi) ranging from 22% to 81%. At phi = 81% and 65%, the MCLC segments form cylinders and spheres, respectively, embedded in an SCLC matrix. At phi 56%, block copolymers form lamellar microdomains in which each segment forms smectic layers parallel to the lamellae. Whereas MCLC segments are mostly extended along the lamella normal but are folded to fit within the lamellae, the SCLC segment backbone is more elongated, traversing the smectic layers. Such backbone dimensions and mesogens' orientation in the SCLC segment are explained in light of the small interfacial area with the B5 segment, which is conserved even when the SCLC segment is in the isotropic liquid state.