Positive Tie Line Slopes as Positive Evidence for the Preferential Interaction Mechanism in Poly(<italic style="font-style: italic">N</italic>-isopropylacrylamide) Co-nonsolvency

Zhong-Fu Yuan; Heng-Zhi You; Yu-Tao Zhang; Peng-Fei Zhang; Hao Liu

doi:10.1007/s10118-026-3750-2

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Positive Tie Line Slopes as Positive Evidence for the Preferential Interaction Mechanism in Poly(N-isopropylacrylamide) Co-nonsolvency

RESEARCH ARTICLE | Updated：2026-07-20

- Positive Tie Line Slopes as Positive Evidence for the Preferential Interaction Mechanism in Poly(N-isopropylacrylamide) Co-nonsolvency
- Chinese Journal of Polymer Science Vol. 44, Pages: 1-9(2026)
- Affiliations：
  
  State Key Laboratory of Advanced Fiber Materials, Center for Advanced Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China
- Author bio：
  
  pfzhangphy@dhu.edu.cn (P.F.Z.)
  liuh@dhu.edu.cn (H.L.)
- Funds：
- DOI：10.1007/s10118-026-3750-2
  CLC：
- Received：18 April 2026，
  
  Accepted：17 May 2026，
  
  Online First：20 July 2026，
  
  Published：2026-06
- Accepted：
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Yuan, Z. F.; You, H. Z.; Zhang, Y. T.; Zhang, P. F.; Liu, H. Positive tie line slopes as positive evidence for the preferential interaction mechanism in poly(N-isopropylacrylamide) co-nonsolvency. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-026-3750-2

Zhong-Fu Yuan, Heng-Zhi You, Yu-Tao Zhang, et al. Positive Tie Line Slopes as Positive Evidence for the Preferential Interaction Mechanism in Poly(N-isopropylacrylamide) Co-nonsolvency[J/OL]. Chinese Journal of Polymer Science, 2026, 441-9. DOI: 10.1007/s10118-026-3750-2.
Yuan, Z. F.; You, H. Z.; Zhang, Y. T.; Zhang, P. F.; Liu, H. Positive tie line slopes as positive evidence for the preferential interaction mechanism in poly(N-isopropylacrylamide) co-nonsolvency. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-026-3750-2 DOI：

Zhong-Fu Yuan, Heng-Zhi You, Yu-Tao Zhang, et al. Positive Tie Line Slopes as Positive Evidence for the Preferential Interaction Mechanism in Poly(N-isopropylacrylamide) Co-nonsolvency[J/OL]. Chinese Journal of Polymer Science, 2026, 441-9. DOI: 10.1007/s10118-026-3750-2. DOI：

摘要

Abstract

The co-nonsolvency of polymers in binary mixtures of individually good solvents remains mechanistically controversial

despite extensive research over several decades. Recent theoretical analyses based on ternary solution thermodynamics suggest that the orientation of tie lines in the polymer solvent composition plane serves as a decisive signature to distinguish between preferential interaction-driven and solvent cosolvent attraction-driven mechanisms

yet direct experimental verification of this prediction has remained elusive. Here

we report the quantitative experimental determination of tie line orientations in a poly(

-isopropylacrylamide) water-methanol system through direct measurement of solvent partitioning between coexisting liquid phases. Our experimental results reveal that all measured tie lines consistently exhibit positive slopes in the polymer concentration and methanol fraction composition planes

unambiguously indicating preferential enrichment of the better solvent in the polyme

r-rich phase. This observation provides direct experimental evidence supporting the preferential interaction-driven mechanism and establishes tie line orientation as a robust practical experimental observable for elucidating co-nonsolvency phenomena. These findings validate theoretical predictions within the Flory-Huggins framework and bridge the gap between the mean field theory and experimental reality

offering a definitive methodology that should broadly applicable to other polymer systems exhibiting similar phase separation behavior.

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Positive Tie Line Slopes as Positive Evidence for the Preferential Interaction Mechanism in Poly(N-isopropylacrylamide) Co-nonsolvency

DOI：10.1007/s10118-026-3750-2

摘要

Abstract

关键词

Keywords

references