Construction of photoresponsive supramolecular micelles based on ethyl cellulose graft copolymer

In this work, a UV-Visible light controlled supramolecular system based on ethyl cellulose (EC) was constructed, combining the host-guest interaction of β-cyclodextrin (β-CD) group and trans-isomer of azobenzene (tAzo) group. To link β-CD to the hydrophobic section, renewable EC was used as macroinitiator to initiate the polymerization of e-caprolactone (e-CL) to form biocompatible and biodegradable comb copolymer EC-g-PCL, and β-CD was attached to the end of PCL side chain via click reaction. Meanwhile, hydrophilic PEG-tAzo was obtained by N,N'-dicyclohexylcarbodiimide (DCC) coupling. Then, the structures of the products were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Subsequently, with the formation of inclusion complexes by β-CD and tAzo groups, the obtained EC-g-PCL-β-CD/PEG-tAzo supramolecular system self-assembled in water with hydrophobic EC-g-PCL-β-CD as core and hydrophilic PEG-tAzo as shell. Furthermore, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to investigate the particle size and size distribution, while NMR and UV-Vis spectra were applied to explore the UV-Visible light stimuli-responsiveness of the micelles.