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Issue 35, 2015
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Understanding the UCST-type transition of P(AAm-co-AN) in H2O and D2O: dramatic effects of solvent isotopes

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Abstract

The UCST-type transition of poly(acrylamide-co-acrylonitrile) (P(AAm-co-AN)) (molar fraction of AN: 13.3%; PDI = 3.2) in H2O and D2O is explored and compared by applying turbidity, DLS as well as FTIR measurements. The transition temperature of P(AAm-co-AN) in D2O is observed to be almost 10 °C higher than that in H2O at the same concentration, demonstrating a dramatic solvent isotope effect. Such a phenomenon could be rooted from a stronger interaction among polymer chains in D2O than in H2O, as indicated from DLS results. It is also observed in second-derivative analysis of FTIR spectra in the ν(C[double bond, length as m-dash]O) region, where all C[double bond, length as m-dash]O groups participate in the formation of inter-/intra-chain hydrogen bonds (C[double bond, length as m-dash]O⋯H–N) in D2O while there is still part of relatively “free” C[double bond, length as m-dash]O groups in H2O. Moreover, we find in the temperature-dependent FTIR spectra that C[triple bond, length as m-dash]N groups exhibit hydrating behavior while C[double bond, length as m-dash]O groups present increased inter-/intra-molecular hydrogen bonding interaction (C[double bond, length as m-dash]O⋯H–N) upon cooling, revealing the later process to be the driving force of the UCST-type transition.

Graphical abstract: Understanding the UCST-type transition of P(AAm-co-AN) in H2O and D2O: dramatic effects of solvent isotopes

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Supplementary files

Article information


Submitted
15 Jul 2015
Accepted
28 Jul 2015
First published
28 Jul 2015

Soft Matter, 2015,11, 7059-7065
Article type
Paper

Understanding the UCST-type transition of P(AAm-co-AN) in H2O and D2O: dramatic effects of solvent isotopes

L. Hou and P. Wu, Soft Matter, 2015, 11, 7059
DOI: 10.1039/C5SM01745A

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