Preparation and characterization of novel side-chain azobenzene polymers containing tetrazole group

A novel methacrylate monomer containing azobenzene chromophore and tetrazole moiety, 4′-(2-methacryloxyethyl)methylamino-4-(5-chlorotetrazol-1-yl)azobenzene (MACA), was synthesized and polymerized to form homopolymer (PMACA) via reversible addition-fragmentation chain transfer (RAFT) polymerization using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as the RAFT agent and azobisisobutyronitrile (AIBN) as an initiator in dimethyl formamide (DMF) solution. Meanwhile, block copolymers (PMMA-b-PMACAs) were successfully obtained by RAFT polymerization of MACA using PMMA as the macro-RAFT agent and AIBN as an initiator. Gel permeation chromatography (GPC) characterization indicated that polymers with well-controlled molecular weights and narrow molecular weight distributions (Mw/Mns < 1.30) were obtained. The structures of these polymers were characterized by 1H NMR and FT-IR spectra. Thermal and photoisomerization behaviors of the polymers indicated that these polymers were amorphous state with good heat stability and photoisomerization performance. Relationship between the electrochemical behavior of block copolymer (PMMA-b-PMACA) and the photoisomerization of azobenzene was investigated by cyclic voltammetry (CV) in chloroform solution, which showed that the oxidation peak of copolymer shifted from 1.0 V to 0.6 V during azobenzene isomerization from trans to cis form. Furthermore, surface relief gratings (SRGs) formed on the films of PMMA-b-PMACAs were also investigated with illumination of a linearly polarized Kr+ laser beam. The diffraction efficiency of the SRGs was 1.22 (PMMA-b-PMACA1), 2.38 (PMMA-b-PMACA2) and 3.02 (PMMA-b-PMACA3), respectively, which increased with the azobenzene contain for the copolymers.