Plasticization of Butyl Methacrylate–Methacrylic Acid Copolymer by Dimethyl Phthalate for Designing Transdermal Therapeutic Systems

The effect of a crystallizing plasticizer dimethyl phthalate on the glass transition temperature of butyl methacrylate copolymer with methacrylic acid (7.6 mol %) is studied in the range of 80–450 K by differential thermal analysis. The solubility of dimethyl phthalate in the copolymer at the melting temperature of the plasticizer is determined by calorimetry. Using the obtained experimental data the diagram of the physical states of the system acrylic copolymer–dimethyl phthalate is plotted and analyzed. The plasticizing characteristics of two plasticizers, dimethyl phthalate and di-2-ethylhexyl phthalate, are compared.