Long-term structural changes in pH-sensitive hydrogels

C. Pamela De Moor, Lisa Doh, Ronald A. Siegel

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11 Scopus citations


The long-term swelling properties of lightly cross-linked copolymer hydrogels consisting of methyl methacrylate (MMA) and N,N-dimethylaminoethyl methacrylamide (DMAA) were studied as a function of pH at 25°C and 37°C. In acidic pH regions, the swelling equilibria were found to be stable over 200 d. In alkaline pH environments, however, the 'equilibrium' swelling increases slowly with time. Gas chromatography of the supernatant shows that substantial methanol is produced, along with trace amounts of N,N-dimethylethylene diamine. Thus, the primary mechanism underlying the structural changes appears to be hydrolysis of ester groups in the MMA side-chains, with a much smaller contribution due to amidolysis of the DMAA side-chains. The implications of these structural changes for the application of this hydrogel, as well as other related hydrogels as long-term implantable biomaterials, are discussed.

Original languageEnglish (US)
Pages (from-to)836-840
Number of pages5
Issue number9
StatePublished - Nov 1991

Bibliographical note

Funding Information:
This work was supported by NIH Grant OK38035 and a grant from the Whitaker Foundation. We thank S. Bozhenko and 2. Yang for assistance.


  • Copoly (MMA-DMAA)
  • hydrogels
  • pH-sensitivity
  • swelling


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