A novel hyperbranched polyester functionalized with azo chromophore: synthesis and photoresponsive properties |
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Authors: | Guojie Wang Xiaogong Wang |
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Affiliation: | (1) Department of Chemical Engineering, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China Fax: 86-10-62770304, e-mail: wxg-dce@mail.tsinghua.edu.cn, CN |
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Abstract: | Summary
A hyperbranched polymer containing azo chromophores on the periphery has been synthesized from transesterification reaction
between a hyperbranched polyester bearing peripheral hydroxyl groups and ethyl 4-{4'-N, Ndi(hydroxyethyl)aminobutoxy]phenylazo}benzoate. The hyperbranched polyester was obtained by adding the AB2 monomers step by step to a multifunctional core molecule. Narrow molecular weight distribution, with a polydispersity index
as low as 1.1, was achieved by this method. The azobenzene- functionalized hyperbranched polymer as well as the corresponding
azo monomer showed typical photoresponsive behavior of an azobenzene type molecule. The trans azobenzene units of the hyperbranched
polymer could be reversibly switched by UV irradiation to the cis form that recovered slowly to the trans form in the dark.
However, significantly less conversion from the trans isomer to the cis isomer was observed for the azobenzenefunctionalized
hyperbranched polymer at the photostationary states under the irradiation of UV light, which could be attributed to the increased
steric hindrance in the hyperbranched polymer.
Received: 1 April 2002 /Revised version: 10 July 2002/ Accepted: 15 July 2002 |
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