Effect of urea on the conformational behavior of poly(N-isopropylacrylamide) |
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| Authors: | Y Fang J-C Qiang D-D Hu M-Z Wang Y-L Cui |
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| Institution: | (1) The Polymer Laboratory Department of Chemistry Shaanxi Normal University Xi' an 710062 People's Republic of China e-mail: yfang@snnu.edu.cn Tel.: +86-29-5307534 Fax: +86-29-5307025, CN |
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| Abstract: | The effect of urea on the conformational behavior of poly(N-isopropylacrylamide) (PNIPAM) in dilute aqueous solution has been investigated using fluorescence spectroscopy, fluorescence
quenching and fluorescence anisotropy measurements via pyrene (Py) probe and acenaphthylene (ACE) label studies. It was demonstrated
that urea promotes the partitioning of the hydrophobic probe, Py, towards the bulk aqueous phase at temperatures above the
lower critical solution temperature (LCST) of the polymer due to swelling of the compact coil conformation. However, the compact
coil structure of the polymer at temperatures greater than its LCST is not completely destroyed, even for urea concentrations
up to 3 M, at which the phase transition is hardly observed. As expected, urea has little effect on the conformational behavior
of PNIPAM at temperatures below its LCST.
Received: 9 February 2000/Accepted: 13 June 2000 |
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| Keywords: | Poly(N-isopropylacrylamide) Urea Pyrene Fluorescence technique Conformation |
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