VISCOELASTIC STUDY OF PH-RESPONSIVE HYDROGELS

The viscoelastic behavior of two pH-sensitive hydrogels hydroxyethyl methacrylate dimethyl aminoethyl methacrylate (HEMA - DMAEMA) and hydroxyethyl methacrylate acrylic acid (HEMA-AA) in acidic and basic mediums were studied. The three-dimensional network structure of hydrogels along with high water content make them an ideal bio-material. The hydrogels were prepared by co-polymerization of one inert and one stimuli-responsive monomer. The structural characterization of hydrogels is needed due to its bio-medical applications. Large amplitude oscillatory shear tests were conducted on the hydrogel samples using a rheometer to find the energy dissipated. The degree of viscous behavior can be determined by the amount of energy dissipated in the material. The LAOS test helps in better understanding of the non-linear visco-elastic behavior of a material. The result obtained showed an increase in the energy dissipation with the increase in the shear strain unique to both the buffer solutions. The energy dissipation obtained for the HEMA-DMAEMA samples was greater in 11.0 pH buffer solution as compared to 3.0 pH buffer solution and the opposite for HEMA-AA samples. The results helped in further understanding the material properties of the two hydrogels. Temperature imposed relaxation tests were also conducted on the HEMA-DMAEMA samples which is to be a part of a much larger project