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 ε-caprolactone （ε-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.
In this paper, three different kinds of β-CD derivatives were synthesized as atom transfer radical polymerization（ATRP） initiator or reversible addition-fragmentation chain transfer polymerization（RAFT） chain transfers. The degree of substitution for each derivative was carefully characterized through 1H-NMR, 13C-NMR spectroscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry（MALDI-TOF-MS）. The factors influencing the degree of substitution were discussed. Moreover, the comparison between ATRP and RAFT was shown in the polymerization of Nisopropyl acrylamide（NIPAM）.
