Liquid-crystalline diblock copolymers produced by living cationic and anionic polymerizations

Two series of liquid-crystalline block copolymers have been synthesized. These polymeric systems consist of an amorphous block and a mesogenic side-chain block. The first system is formed by poly(n-butylvinyl ether) (poly(BVE)) as an amorphous block and poly(6-((4-cyano-4′-biphenyl)oxy)hexylvinyl ether) as the liquid-crystalline block. The second system is formed by poly(styrene) (PS) and poly(6-((4-cyano-4′-biphenyl)oxy)hexyl methacrylate). In both systems the mesogenic unit is the same but the polymeric main chains are different. The polymers were prepared by a living polymerization method, cationic in the case of vinyl ethers and anionic in the case of the styrene/methacrylate system, which resulted in materials with well-defined molecular weights and narrow molecular weight distributions. The block copolymers exhibit smectic polymorphism, which has been characterized by means of optical microscopy, DSC, and X-ray diffraction. The microphase-separated character of these block copolymers has been proved by means of small-angle X-ray scattering studies and transmission electron microscopy (TEM).