中国物理B ›› 2016, Vol. 25 ›› Issue (7): 74703-074703.doi: 10.1088/1674-1056/25/7/074703

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Role of hydrogen bonding in solubility of poly(N-isopropylacrylamide) brushes in sodium halide solutions

Xin-Jun Zhao(赵新军), Zhi-Fu Gao(高志福)   

  1. 1 Xinjiang Laboratory of Phase Transitions and Microstructures of Condensed Matter Physics, YiLi Normal University, Yining 835000, China;
    2 National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China 3Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, China
  • 收稿日期:2015-09-05 修回日期:2016-02-13 出版日期:2016-07-05 发布日期:2016-07-05
  • 通讯作者: Xin-Jun Zhao E-mail:zhaoxinjunzxj@163.com
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 21264016, 11464047, and 21364016) and the Joint Funds of Xinjiang Natural Science Foundation, China (Grant No. 2015211C298).

Role of hydrogen bonding in solubility of poly(N-isopropylacrylamide) brushes in sodium halide solutions

Xin-Jun Zhao(赵新军)1,2, Zhi-Fu Gao(高志福)3   

  1. 1 Xinjiang Laboratory of Phase Transitions and Microstructures of Condensed Matter Physics, YiLi Normal University, Yining 835000, China;
    2 National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China 3Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, China
  • Received:2015-09-05 Revised:2016-02-13 Online:2016-07-05 Published:2016-07-05
  • Contact: Xin-Jun Zhao E-mail:zhaoxinjunzxj@163.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 21264016, 11464047, and 21364016) and the Joint Funds of Xinjiang Natural Science Foundation, China (Grant No. 2015211C298).

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摘要： By employing molecular theory, we systematically investigate the shift of solubility of poly(N-isopropylacrylamide) (PNIPAM) brushes in sodium halide solutions. After considering PNIPAM-water hydrogen bonds, water-anion hydrogen bonds, and PNIPAM-anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series: NaCl >NaBr >NaI. PNIPAM-water hydrogen bonds are affected by water-anion hydrogen bonds and PNIPAM-anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series.

关键词: molecular theory, PNIPAM brushes, anion effect, hydrogen bonds

Abstract: By employing molecular theory, we systematically investigate the shift of solubility of poly(N-isopropylacrylamide) (PNIPAM) brushes in sodium halide solutions. After considering PNIPAM-water hydrogen bonds, water-anion hydrogen bonds, and PNIPAM-anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series: NaCl >NaBr >NaI. PNIPAM-water hydrogen bonds are affected by water-anion hydrogen bonds and PNIPAM-anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series.

Key words: molecular theory, PNIPAM brushes, anion effect, hydrogen bonds

中图分类号:  (Statistical theories and models)

  • 47.27.eb
05.65.+b (Self-organized systems)