Hierarchical nanostructures of a liquid crystalline block copolymer with a hydrogen-bonded calamitic mesogen

With a pyridine derivative containing a calamitic mesogen 4-((6-((4'-((4-hexylphenyl)ethynyl)-[1,1'-biphenyl]-4-yl)oxy)hexyl)oxy)pyridine (HEBC6) used as the hydrogen-bonding acceptor and polydimethylsiloxane-b-poly (2,5-bis(4-carboxy phenyl)styrene) (PDMS-b-PM3H) as the hydrogen-bonding donor, a series of supramolecular liquid crystalline block copolymers (SLCBCPs) were prepared through hydrogen bonding. In the supramolecular block, the calamitic mesogen was decoupled from the motion of PM3H chains by using a flexible spacer. Different microphase-separated nanostructures and liquid crystalline (LC) structures were obtained by varying the degree of polymerization of the PM3H block and the molar ratio of HEBC6 to PDMS-b-PM3H. The SLCBCPs can self-assemble into hexagonally packed cylinders (HEX), lamellae (LAM), and inverted HEX. Smectic A phase and parallel packing of the calamitic mesogens were also observed on a smaller length scale, and these two ordered structures are synergistic and promotional. Therefore, hierarchically ordered structures can be obtained from these SLCBCPs.