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Long-term structural changes in pH-sensitive hydrogels.

Authors
  • De Moor, C P1
  • Doh, L
  • Siegel, R A
  • 1 Department of Pharmacy, University of California, San Francisco 94143-0446.
Type
Published Article
Journal
Biomaterials
Publisher
Elsevier
Publication Date
Nov 01, 1991
Volume
12
Issue
9
Pages
836–840
Identifiers
PMID: 1764554
Source
Medline
Language
English
License
Unknown

Abstract

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 degrees C and 37 degrees 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.

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