Electrolytically Activated Contractile Polymer


FOR several years it has been known that certain types of polymers, ‘chemical muscles’, change dimensions depending on their chemical environment1. A typical one is that prepared as a co-polymer of polyvinyl alcohol (PVA) and polyacrylic acid (PAA)2. This polymer swells or shrinks osmotically depending on the total ionic concentration inside the polymer. This is determined primarily by the degree of ionization of the weak carboxylic acid groups. When the external solution is acidic the degree of dissociation is low and the polymer shrinks. In alkaline solution it expands. This has been referred to as the ‘pH muscle’2.

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  1. 1

    Kuhn, W., Hargitay, B., Katchalsky, A., and Eisenberg, H., Nature, 165, 525 (1950).

  2. 2

    Kuhn, W., Ramel, A., and Walters, D. H., Size and Shape Changes of Contractile Polymers, edit. by Wasserman, A., 41 (Pergamon Press, New York, 1960).

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HAMLEN, R., KENT, C. & SHAFER, S. Electrolytically Activated Contractile Polymer. Nature 206, 1149–1150 (1965). https://doi.org/10.1038/2061149b0

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