Hydrogen-Bonding-Mediated Formation of Supramolecular Rod−Coil Copolymers Exhibiting Hexagonal Columnar and Bicontinuous Cubic Liquid Crystalline Assemblies

The preparation and characterization of the supramolecular rod−coil copolymers directed by molecular recognition of 4,4‘-bipyridine and 4-[poly(propyleneoxy)propyloxy]-4‘-bis(biphenyl carboxylic acid) with degrees of polymerization (DP) of poly(propylene oxide) coil of eight ( P-8-HP ), 10 ( P-10-HP ), 15 ( P-15-HP ), 17 ( P-17-HP ), 21 ( P-21-HP ), 27 ( P-27-HP ) and 34 ( P-34-HP ) are described. The introduction of poly(propylene oxide) (PPO) coils with different lengths into the rodlike polymeric system induces a rich variety of self-assembled microstructures. In the crystalline phase, the supramolecular rod−coil copolymers with DP of PPO 8−17 organize into a microphase-separated monolayer lamellar structure. In contrast, the supramolecular rod−coil copolymers with DP of PPO 21−34 exhibit a hexagonal columnar crystalline phase. A dramatic phase change after crystalline melting of the polymers is observed with the variation of the coil length. The supramolecular rod−coil copolymers P-8-HP and P-10-HP display a bicontinuous cubic mesophase with Ia 3 d symmetry, while the supramolecular rod−coil copolymers P-15-HP, P-17-HP, and P-21-HP with a medium length of PPO coil exhibit a hexagonal columnar mesophase. Further increasing the length of coil, as in the case of P-27-HP and P-34-HP, suppresses liquid crystallinity and induces only crystalline polymers.