Preparation and characterization of hydrogen-bonded P4VP-bisazobenzene complexes

Photoresponsive supramolecular complexes contain 4-hydroxyethyloxy-4'-(4-nitrophenylazo)azobenzene (BisAzo) molecule as a hydrogen bonding donor and poly (4-vinylpyridine) (P4VP) as a hydrogen bonding acceptor, and strong phenol pyridine hydrogen bonding is formed between them. FT-IR spectrum verifies the hydrogen bonding has formed between the phenol hydroxyl of BisAzo and pyridine ring of P4VP. The glass-transition temperature (T-g) is determined with differential-scanning calorimetry (DSC) and a decrease of complexes compared with pure P4VP is observed due to the attachment of BisAzo onto the backbone of P4VP. Polarized optical microscopy (POM) is performed to study the structure of supramolecular complexes, with a different texture observed which is different from both constituents alone. X-ray diffraction patterns are investigated with the same films already used for POM observation, indicating a lamellar structure with a periodic thickness of 4.1 nm. The supramolecular complexes P4VP/(BisAzo)(x) are prepared with the molar ratio of BisAzo to the pyridine group varied at x=0.25, 0.5, 0.75 and 1.0, no mass aggregation is observed even at a high concentration of chromophore.