- Synthesis and photoresponsive behavior of the high-Tg azobenzene polymers via RAFT polymerization
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Well-defined photo-responsive alternating copolymers, poly(4-(N-maleimido) azobenzene-alt-styrene)s (PMSts), were successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A divinyl monomer was used in this polymerization to prepare high molecular weight azobenzene polymers. These polymers had good solubility in most organic solvents, formed films well, and had high glass transition temperatures (Tg = 174-250 °C) and were heat resistant (Td > 320 °C). The photo-induced trans-cis isomerization of the copolymers was examined in chloroform solution. Surface-relief-gratings (SRGs) formed on the polymer films were also investigated using illumination from a linearly polarized Kr + laser beam.
- Xue, Xiaoqiang,Zhu, Jian,Zhang, Zhengbiao,Zhou, Nianchen,Zhu, Xiulin
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- Preparation and Insights of Smart Foams with Phototunable Foamability Based on Azobenzene-Containing Surfactants
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Smart foams with tunable foamability exhibit superb applications in many fields such as colloidal and interface science. Herein, we have synthesized an azobenzene-containing surfactant with excellent photoresponsiveness by a simple thiol-maleimide click reaction between thioglycolic acid and 4-(N-maleimide) azobenzene (MAB). The structure and the photoresponsive behavior of the novel surfactant are characterized. Depending on the solution concentration, the synthesized surfactant demonstrated various speeds for the trans/cis photoisomerization varying from 9 to 24 s for the given concentration range and excellent reversible photoisomerization cycling stability (more than 20 cycles) upon light irradiation. Based on these conformational switches, a series of phototriggered obvious surface properties (e.g., critical micelle concentration (CMC), surface tension (?), and surface excess concentration (?)) changes of the surfactant are achieved. More specifically, the smart foam system with tunable foamability is realized. As-formed smart foams with rapid photocontrolled reversible foaming/defoaming transition and excellent cycling stability make them very attractive candidates for applications in wastewater treatment, green textile, oil extraction, and emulsification.
- Zhai, Congcong,Azhar, Umair,Yue, Wence,Dou, Yingqian,Zhang, Luqing,Yang, Xiaoyu,Zhang, Yabin,Xu, Peiming,Zong, Chuanyong,Zhang, Shuxiang
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- Responsive behavior of 4-(N-maleimido)azobenzene in polymers with aromatic main chain and side chain linked units
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Polymer matrices with aromatic main chain and side chain linked units (polystyrene, polysulfone) were employed to construct thin films containing maleimidoazobenzene molecules in order to develop new materials with responsive properties. The photochromic behavior of the active compound was studied both in the solid and solution state for comparison. The thermal cis-trans isomerization of azobenzene chromophores in polymer films follows two different kinetic pathways. A double-exponential relaxation process (fast and slow) took place in polystyrene matrix under 70 °C while the thermal isomerization at 70 °C and higher follows a first-order kinetics. The cis isomer content corresponding to the photostationary state was found to be lower in polymer films than in solution.
- Airinei, Anton,Rusu, Elena,Barboiu, Virgil
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experimental part
p. 489 - 495
(2010/08/06)
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