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Acta Phys. -Chim. Sin.  2010, Vol. 26 Issue (07): 1915-1922    DOI: 10.3866/PKU.WHXB20100728
PHOTOCHEMISTRY AND SPECTROSCOPY     
Solubility of Poly(N-isopropylacrylamide) in Aqueous Methanol from Raman Spectroscopy
ZHAO Rong-Li, LIN Ke, ZHOU Xiao-Guo, LIU Shi-Lin
Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, P. R. China
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Abstract  

We measured the non-coincidence effect (NCE) in the Raman spectrum of poly(N-isopropylacrylamide) (PNIPAM) in aqueous methanol at -13 ℃ (below the lower critical solution temperature, LCST). This was done to investigate the solubility of PINPAM in aqueous methanol by considering molecular interactions. Changes of NCE when adding PNIPAM to an aqueous methanol solution show that at the molar fraction of methanol x=1.0-0.90, PNIPAMpreferentially adsorbs methanol and at x=0.80-0.50, PNIPAMpreferentially adsorbs water. At x=0.50-0.20, PNIPAM breaks down the ring structure composed of two methanol molecules and one water molecule. Further comparison between the changes of NCE when adding PNIPAM and its monomer NIPPA indicates that PNIPAM adsorbs methanol cooperatively through hydrophobic interactions. This cooperative interaction breaks down the methanol-water ring structure at low methanol concentrations. The cononsolvency phenomenon of PNIPAM in a methanol solution when heating above the LCST temperature is attributed to a reformation of the methanol-water ring structure.



Key wordsRaman spectroscopy      PNIPAMpolymer      Aqueous methanol      Noncoincidence effect      Solubility      Cooperative     
Received: 24 March 2010      Published: 31 May 2010
MSC2000:  O645  
Corresponding Authors: LIU Shi-Lin     E-mail: slliu@ustc.edu.cn
Cite this article:

ZHAO Rong-Li, LIN Ke, ZHOU Xiao-Guo, LIU Shi-Lin. Solubility of Poly(N-isopropylacrylamide) in Aqueous Methanol from Raman Spectroscopy. Acta Phys. -Chim. Sin., 2010, 26(07): 1915-1922.

URL:

http://www.whxb.pku.edu.cn/10.3866/PKU.WHXB20100728     OR     http://www.whxb.pku.edu.cn/Y2010/V26/I07/1915

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