Visible-light-responsive polymeric multilayers for trapping and release of cargoes via host–guest interactions

A novel visible light responsive polymeric multilayer was constructed by layer-by-layer (LbL) electrostatic self-assembly, from which the trapping/release of cargoes via azobenzene/cyclodextrin-based host–guest interactions could be realized upon light stimulation. Visible light responsive poly{6-[(2,6-dimethoxyphenyl)azo-4-(2′,6′ dimethoxy)phenoxy]propyl dimethylaminoethyl methacrylate-random-poly(2-(N,N-dimethylaminoethyl) methacrylate)} (Azo-PDMAEMA) was synthesized, which was used as a polycation to combine with polyacrylic acid (PAA) for the construction of multilayers through the LbL electrostatic self-assembly technique. The cargo molecules, cyclodextrins modified with rhodamine B, could be loaded into the multilayers via the interaction between the trans azobenzene and cyclodextrin. Green light would induce isomerization of azobenzene from the trans-configuration to the cis, which disassembled the host–guest complex and resulted in the release of cargoes from the multilayers. Upon blue light irradiation, the cis azobenzene could recover to the trans form, thus a stable inclusion complex would be formed and the cargoes could be reloaded into the multilayers again. It is noted that the visible-light-controlled trapping/release of cargoes from the multilayers could be reconstructed reliably and conveniently. The electrostatically self-assembled multilayers of the prepared azobenzene-functionalized polymers combined with cyclodextrin show great potential in reversible trapping and release of cargoes controlled by visible light.