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Interaction of Urea with Pluronic Block Copolymers by ¹H NMR Spectroscopy

Jun-he Ma,^† Chen Guo,*^† Ya-lin Tang,^‡ Lin Chen,^† P. Bahadur,^§ and Hui-zhou Liu*^†

Laboratory of Separation Science and Engineering, State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100080, People's Republic of China, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China, and Department of Chemistry, V. N. South Gujarat University, Surat 395007, Gujarat, India

J. Phys. Chem. B, 2007, 111 (19), pp 5155–5161

DOI: 10.1021/jp070887m

Publication Date (Web): April 17, 2007

†

Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences.

To whom correspondence should be addressed. Phone: +86-10-62555005. Fax: +86-10-62554264. E-mail: cguo@home.ipe.ac.cn or hzliu@home.ipe.ac.cn.

‡

Institute of Chemistry, Chinese Academy of Sciences.

V. N. South Gujarat University.

Abstract

Solution ¹H NMR techniques were used to characterize the interaction of urea with poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) triblock copolymers. The urea was established to interact selectively with the PEO blocks of the block copolymer, and the interaction sites were found not to change with increasing temperature. Such interactions influence the self-assembly properties of the block copolymer in solution by increasing the hydration of the block copolymers and stabilizing the gauche conformation of the PPO chain. Therefore, urea increases the critical micellization temperature (CMT) values of PEO−PPO−PEO copolymers, and the effect of urea on the CMT is more pronounced for copolymers with higher PEO contents and lower for those with increased contents of PPO segments.

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