Dissociation behavior of poly(α-hydroxy acrylic acid)

Authors

  • Toru Tamura,

    1. Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
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  • Hiroshi Uehara,

    1. Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
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  • Kenji Ogawara,

    1. Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
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  • Susumu Kawauchi,

    1. Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
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  • Mitsuru Satoh,

    Corresponding author
    1. Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
    • Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
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  • Jiro Komiyama

    1. Department of Polymer Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
    Current affiliation:
    1. Department of Life Environment, Jissen Women's University, Osakaue, Hino, Tokyo 191-0061, Japan
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Abstract

Dissociation behavior of poly(α-hydroxy acrylic acid) (PHA) was investigated by potentiometric titration in the presence of NaCl and/or divalent metal chlorides. It was found that pH values of PHA aqueous solutions increased with time when the degree of dissociation, α, is high (α ≧ 0.5 for NaCl system) and decreased in the lower α region (α < 0.5 for NaCl). The increase of pH was attributed to lactone ring formation that occurs between a carboxyl group and a neighbor hydroxyl group upon protonation to the former, and the decrease of pH to an induction effect by lactone ring to −COOH group. The pH-increasing process was analyzed by assuming it being of a first order to obtain a time constant. On the basis of time constant thus estimated and pKa values for divalent counterion systems, a correlation between counterion binding and lactone ring formation was discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1523–1531, 1999

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