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Title: Temperature-responsive polymers in mixed solvents: Competitive hydrogen bonds cause cononsolvency
Authors: Tanaka, Fumihiko
Koga, Tsuyoshi  kyouindb  KAKEN_id
Winnik, Francoise M.
Issue Date: 11-Jul-2008
Publisher: American Physical Society (APS)
Journal title: Physical Review Letters
Volume: 101
Issue: 2
Thesis number: 028302
Abstract: If two good solvents become poor for a polymer when mixed, the solvent pair is called a cononsolvent pair. The sharp reentrant coil-to-globule-to-coil transition of a poly(N-isopropylacrylamide) chain observed in the mixed solvent of water and methanol is shown to be caused by the competitive hydrogen bonding by water and methanol molecules onto the polymer chain. On the basis of a new statistical-mechanical model for competitive hydrogen bonds, the mean square end-to-end distance is theoretically calculated and compared with experiment. The chain sharply collapses at the molar fraction xm0.2 of methanol, stays collapsed up to xm0.4, and finally recovers the swollen state at xm0.6. Such a reentrant coil-globule transition takes place because the total number of hydrogen bonds along the chain exhibits a similar square-well-type depression as a result of the competition.
Rights: © 2008 The American Physical Society
URI: http://hdl.handle.net/2433/84643
DOI(Published Version): 10.1103/PhysRevLett.101.028302
PubMed ID: 18764232
Related Link: http://link.aps.org/doi/10.1103/PhysRevLett.101.028302
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