Synthesis of novel side-chain triphenylamine polymers with azobenzene moieties via RAFT polymerization and investigation on their photoelectric properties

摘要

Two novel and well-defined polymers, poly[6-(5-(diphenylamino)-2-((4- methoxyphenyl)diazenyl)phenoxy)hexyl methacrylate] (PDMMA) and poly[6-(4-((3-ethynylphenyl)diazenyl) phenoxy)hexyl methacrylate] (PDPMMA), which bear triphenylamine (TPA) incorporated to azobenzene either directly (PDMMA) or with an interval (PDPMMA) as pendant groups were successfully prepared via reversible addition-fragmentation chain transfer polymerization technique. The electrochemical behaviors of PDPMMA and PDMMA were investigated by cyclic voltammograms (CV) measurement. The hole mobilities of the polymer films were determined by fitting the J-V (current-voltage) curve into the space-charge-limited current method. The influence of photoisomerization of the azobenzene moiety on the behaviors of fluorescence emission, CV and hole mobilities of these two polymers were studied. The fluorescent emission intensities of these two polymers in CH _2Cl _2 were increased by about 100 times after UV irradiation. The oxidation peak currents (I _(OX)) of the PDMMA and PDPMMA in CH _2Cl _2 were increased after UV irradiation. The photoisomerization of the azobenzene moiety in PDMMA had significant effect on the electrochemical behavior, compared with that in PDPMMA. The changes of the hole mobility before and after UV irradiation were very small for both polymers. The HOMO energies (E _(HOMO), HOMO: the highest occupied molecular orbital) of side chain moieties of TPA incorporated with cis-isomer and trans-isomer of azobenzene in PDMMA and PDPMMA were obtained by theoretical calculation, which are basically consistent with the experimental results.