Structural characterization of pH-sensitive acrylic hydrogels prepared for controlled release of drugs


Fabad Journal of Pharmaceutical Sciences, vol.24, no.2, pp.75-81, 1999 (Scopus) identifier

  • Publication Type: Article / Article
  • Volume: 24 Issue: 2
  • Publication Date: 1999
  • Journal Name: Fabad Journal of Pharmaceutical Sciences
  • Journal Indexes: Scopus
  • Page Numbers: pp.75-81
  • Hacettepe University Affiliated: Yes


Crosslinked copolymers of 2-hydroxyethyl methacrylate (HEMA) with varying concentrations or anionic or cationic monomers, i.e., acrylic acid (AA) and dimethylaminoethyl methacrylate (DMAEMA), were prepared by bulk polymerization in the membrane form for possible controlled drug release applications. Surface structures of these copolymers were characterized by the measurement of surface free energy, SEM, XPS, and ATR-FTIR. Their bulk properties were investigated by means of swelling experiments conducted in water and in buffered solutions at various pH values from 2 to 11.90. Thermal and mechanical properties of the copolymers were studied by DSC and DMTA techniques. It was observed that the incorporation of ionic comonomers to HEMA significantly affects both the surface and bulk properties, except the surface free energies and texture. Results indicate that gels having ionizable groups are pH-sensitive and their equilibrium water contents (EWC) strongly depend upon the ionizable monomer content. Increasing the percentage of ionic comonomer in the polymer increases the EWC without changing the time for equilibration. In the case of AA-containing copolymers, a sharp increase of the EWC between pH 5 and 7 is observed. In contrast, a sharp decrease of the EWC between 7 and 8 is observed for DMAEMA-containing gels. The results indicated that these polymeric systems can be considered as good candidates for oral colon-specific delivery of some drugs.