Behaviors of self-assembled diblock copolymer with pendant photosensitive azobenzene segments

A novel monomer, ethyl 4-[4-(11-methacryloyloxyundecyloxy)phenyl azobenzoyl-oxyl] benzoate, containing a photoisomerizable N=N group was synthesized. The monomer was further diblock copolymerized with methyl methacrylate. Amphiphilic diblock copolymer poly(methyl methacrylateblock-ethyl 4-[4-(11-methacryloyloxyundecyloxy)phenyl azobenzoyl-oxyl] benzoate (PMMA-b-PAzoMA) was synthesized using atom transfer radical polymerization. The reverse micelles with spherical construction were obtained with 2 wt % of the diblock copolymer In a THF/H₂O mixture of 1:2. Under alternating UV and visible light Illumination, reversible changes in micellar structure between sphere and rod-like particles took place as a result of the reversible E-Z photoisomerization of azobenzene segments in PMMA-b-PAzoMA. Microphase separation of the amphiphilic diblock copolymer In thin films was achieved through thermal and solvent aligning methods. The microphases of the annealed thin films were investigated using atom force microscopy topology and scanning electron microscopy analyses.