LIQUID-CRYSTALLINE SIDE-CHAIN AB BLOCK-COPOLYMERS BY DIRECT ANIONIC-POLYMERIZATION OF A MESOGENIC METHACRYLATE

AB block copolymers with a liquid-crystalline and an amorphous block are synthesized by anionic copolymerization of 4-[4-(4-methoxyphenylazo)phenoxy]butyl methacrylate (1) with either styrene or methyl methacrylate (MMA). The polymerization of 1 proceeds from polystyrenelithium capped with 1,1-diphenylethylene to produce polystyrene-block-poly(1), while poly(1)-block-PMMA is prepared by addition of MMA to the ''living'' poly(1) anion. A large variety of block copolymers is obtained with narrow molecular weight distribution and definite composition. The mesophase behaviour of these samples is analyzed with respect to the chain length of the liquid-crystalline block. Electron microscopy of a high-molecular-weight polystyrene-block-poly(1) provides direct evidence for a microphase-separated structure composed of spherical polystyrene domains embedded in a liquid-crystalline matrix. For the corresponding poly(1)-block-PMMA, however, electron microscopy indicates no structure, although dynamic mechanical analysis proves microphase separation.