White-Light-Emitting Supramolecular Polymer Gel Based on -CD and NDI Host-Guest Inclusion Complex.

Supramolecular polymer formed by non-covalent interactions between complementary building blocks entraps solvents and develops supramolecular polymer gel. A supramolecular polymer gel was prepared by the heating-cooling cycle of -cyclodextrin (-CD) and naphthalenedimide (NDI) solution in N,N-dimethylformamide (DMF). The host-guest inclusion complex of -CD and NDI containing dodecyl amine forms the supramolecular polymer and gel in DMF. However, -CD and NDI having glutamic acid, fail to form the supramolecular polymer and gel under the same condition. X-ray crystallography shows that the alkyl chains of NDI are complementary to the hydrophobic cavity of the two -CD units. From rheology, the storage modulus was approximately 1.5 orders of magnitude larger than the loss modulus, which indicates the physical crosslink and elastic nature of the thermo-responsive gel. FE-SEM images of the supramolecular polymer gel exhibit flake-like morphology and a dense flake network. The flakes developed from the assembly of smaller rods. Photophysical studies show that the host-guest complex formation and gelation have significantly enhanced emission intensity with a new hump at 550 nm. Upon excitation by a 366 nm UV-light, NDI and -CD gel in DMF shows white light emission. The gel has the potential for the fabrication of organic electronic devices.