Photoswitchable Nanocarrier with Reversible Encapsulation Properties

An amphiphilic dendritic polymer with polyethylenimine (PEI) as the hydrophilic core, steric ester (STA) as the hydrophobic shell, and azobenzene (AZO) groups as the photoswitchable moieties was synthesized via amidation reaction. The synthesized dendritic macromolecule was characterized by 1H nuclear magnetic resonance (NMR), FT-IR spectroscopy, and dynamic light scattering (DLS). With alternating UV and visible-light irradiation, azobenzene moieties of polyethylenimine-steric ester-azobenzene (PEI-STA-AZO) undergo a reversible isomerization between the cis and trans state. The encapsulation tests demonstrated that PEI-STA-AZO with trans-isomer is not capable of encapsulating anionic guests, whereas the one with cis-isomers is able to encapsulate the anionic guests from the aqueous solution to the organic layer. Molecular modeling by Spartan was utilized to explain the special encapsulation property of PEI-STA-AZO. Azobenzene groups functioned as a reversible photo-switch in the dendritic guesthost system, and the reversibility of encapsulation capability of PEI-STA-AZO was also demonstrated.