title: Cucurbit[8]uril-Containing Multilayer Films for the Photocontrolled Binding and Release of a Guest Molecule.
abstract: The powerful host-guest chemistry of cucurbit[8]uril (CB[8]) was employed to obtain photoresponsive polyelectrolyte multilayer films for the reversible and photocontrolled binding and release of an organic guest molecule. For this purpose, we designed and synthesized a polyelectrolyte with azobenzene side groups. Then, CB[8] was associated with the azo side group to obtain a supramolecular host-guest complex that was further used as building block in order to prepare photoresponsive and CB[8]-containing polyelectrolyte multilayer films. Ultraviolet spectroscopy and a dissipative quartz crystal microbalance are employed to monitor the formation of the host-guest complex and the layer-by-layer self-assembly of the multilayer films, respectively. We demonstrate that the photoresponsive properties of the azo side groups are maintained before and after host-guest complexation with CB[8] in solution and within the multilayer films, respectively. A guest molecule was then specifically included as second binding partner into the CB[8]-containing multilayer films. Subsequently, the release of the guest was performed by UV light irradiation due to the trans-cis isomerization of the adjacent azo side groups. Re-isomerization of the azo side groups was achieved by VIS light irradiation and enabled the rebinding of the guest into CB[8]. Finally, we demonstrate that the photocontrolled binding and release within CB[8]-containing multilayer films can reliably and reversibly be performed over a period of more than 2 weeks with constant binding efficiency. Therefore, we expect such novel type of photosensitive films to have promising future applications in the field of stimuli-responsive nanomaterials.
authors.affiliation: Institute of Physical Chemistry, University of Muenster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Nicolas
authors.affiliation: Key Laboratory of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yuan
authors.affiliation: Key Laboratory of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Physical Chemistry, University of Muenster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Schönhoff