Dielectric and microhardness studies of methylene blue doped PMMA matrix

Pure and methylene blue (MB) doped poly(methyl methacrylate) (PMMA) samples were prepared by free radical vinyl polymerization. The effect of methylene blue, which itself is polar in nature, on the glass transition temperature, electric permittivity, and microhardness of the PMMA matrix was studied. It was found that incorporation of the dye increases the electric permittivity and decreases the glass transition temperature of the system. The maximum value of the loss tangent below the glass transition temperature suggests the rotation of the ester side group (β relaxation). MB can also act as a retarder of free radical polymerization causing reduction in the hardness value.