Understanding the effect of chain entanglement on the glass transition of a hydrophilic polymer

Authors

  • Xiaolin Lu,

    Corresponding author
    1. Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China
    • Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China
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  • Gi Xue,

    1. Department of Polymer Science, Nanjing University, Nanjing, 210093, People's Republic of China
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  • Yongli Mi

    Corresponding author
    1. Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
    • Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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Abstract

In this article, we report an interesting phenomenon of the glass transition temperature (Tg) deviation of a hydrophilic polymer. Polyacrylamide (PAL) samples with different extents of chain entanglement were prepared by spray drying and solution casting. We found that the glass transition temperature increases as the extent of chain entanglement decreases upon the sub-Tg annealing. The water content in the PAL matrix is found with no direct correlation to Tg. However, the observation of a faster diffusion process of water in the disentangled PAL matrix offers an evidence of a faster relaxation process of disentangled PAL molecules. The Tg increase of the disentangled PAL samples is believed to be associated with the increased molecular interaction during the chain relaxation process upon the sub-Tg annealing. A macroscopic evidence is the fact that the density of the hot-laminated samples increases as the extent of chain entanglement decreases. A thermodynamic analysis suggests that enthalpy more than entropy favors an elevated Tg of a disentangled hydrophilic polymer upon the sub-Tg annealing. We believe that this research provides new understanding of Tg of the hydrophilic polymers, which are being extensively used in bio-related studies. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

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