Hierarchical Structuresin Lamellar Hydrogen BondedLC Side Chain Diblock Copolymers.

We show that in a hydrogen bonded LC side chain diblockcopolymerwith lamellar morphology on the block copolymer level, two distinctpacking mechanisms of the side chain blocks are possible dependingon the amount of hydrogen bonded side chains. We mixed a hydrogenbonding mesogen, cholesteryl hemisuccinate (CholHS), with poly(1,2-butadiene)-block-poly(2-vinylpyridine) (PBd-P2VP) and poly(styrene)-block-poly(4-vinylpyridine) (PS-P4VP), in which the poly(vinylpyridine)act as host blocks, and we varied the CholHS to pyridine repeat unitratio (x). With all x, a lamellarmorphology on the block copolymer level was achieved. However, atlow binding of CholHS to the host block, the CholHS side chains microphaseseparated into a single layer inside the poly(pyridine) lamellae resultingin a novel microphase separated structure. This includes, for example,the PS-P4VP sample with x= 0.25 and all the PBd-P2VPbased samples since hydrogen bonding of CholHS to P2VP was stericallylimited as revealed by infrared spectroscopy. No such limits werepresent in the rest of the PS-P4VP samples which showed a gradualshift from the single CholHS lamella morphology to exclusively liquidcrystalline smectic layers oriented perpendicular to the block domaininterfaces. [ABSTRACT FROM AUTHOR]