TY - JOUR
T1 - Photoresponsive and fluorescence behaviors of azobenzene-containing amphiphilic block copolymers
AU - Lee, Ting Lei
AU - Lo, Chieh Tsung
N1 - Funding Information:
This work is financially supported by Ministry of Science and Technology in Taiwan under Grant No. 102-2221-E-006-018-MY3 and 105-2628-E-006-009-MY3.
Publisher Copyright:
© 2017 Wiley Periodicals, Inc.
PY - 2017/5/15
Y1 - 2017/5/15
N2 - The effects of solvency and mole fraction of azobenzene moieties (fPAzoMA) on the photoresponsive and fluorescence behaviors of poly(acrylic acid)-block-poly(6-[4-(4′-methoxyphenylazo)phenoxy]hexyl methacrylate) (PAA-PAzoMA) amphiphilic diblock copolymers were investigated using UV–vis spectroscopy and fluorescence spectroscopy. The photoresponsive behavior depended strongly on the solvency and fPAzoMA. When dissolved in a PAA-selective solvent, PAA-PAzoMA formed micelles with PAzoMA in the micelle core. The confinement of azobenzene moieties caused a steric hindrance, thereby markedly reducing the kinetics of photoisomerization compared with that of the unconfined PAA-PAzoMA in a nonselective solvent. Additionally, PAA-PAzoMA dissolved in the PAA-selective solvent caused a blue shift of the maximum absorbance, suggesting the formation of H-aggregates of azobenzene mesogens. The high H-aggregate content substantially reduced the fluorescence emission. Consequently, the fluorescence emission of PAA-PAzoMA in the nonselective solvent was more intense than that in the PAA-selective solvent. Upon UV irradiation, the enhanced bent-shaped cis isomers disturbed the compact packing of azobenzene mesogens, which substantially enhanced the fluorescence emission. Both the photoisomerization rate and fluorescence emission decreased with an increase in fPAzoMA.
AB - The effects of solvency and mole fraction of azobenzene moieties (fPAzoMA) on the photoresponsive and fluorescence behaviors of poly(acrylic acid)-block-poly(6-[4-(4′-methoxyphenylazo)phenoxy]hexyl methacrylate) (PAA-PAzoMA) amphiphilic diblock copolymers were investigated using UV–vis spectroscopy and fluorescence spectroscopy. The photoresponsive behavior depended strongly on the solvency and fPAzoMA. When dissolved in a PAA-selective solvent, PAA-PAzoMA formed micelles with PAzoMA in the micelle core. The confinement of azobenzene moieties caused a steric hindrance, thereby markedly reducing the kinetics of photoisomerization compared with that of the unconfined PAA-PAzoMA in a nonselective solvent. Additionally, PAA-PAzoMA dissolved in the PAA-selective solvent caused a blue shift of the maximum absorbance, suggesting the formation of H-aggregates of azobenzene mesogens. The high H-aggregate content substantially reduced the fluorescence emission. Consequently, the fluorescence emission of PAA-PAzoMA in the nonselective solvent was more intense than that in the PAA-selective solvent. Upon UV irradiation, the enhanced bent-shaped cis isomers disturbed the compact packing of azobenzene mesogens, which substantially enhanced the fluorescence emission. Both the photoisomerization rate and fluorescence emission decreased with an increase in fPAzoMA.
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U2 - 10.1002/polb.24323
DO - 10.1002/polb.24323
M3 - Article
AN - SCOPUS:85013817053
SN - 0887-6266
VL - 55
SP - 793
EP - 803
JO - Journal of Polymer Science, Part B: Polymer Physics
JF - Journal of Polymer Science, Part B: Polymer Physics
IS - 10
ER -