Heat Capacity, Thermodynamic Functions, and the Glass Transition of Butyl Methacrylate–Methacrylic Acid Copolymers

Abstract—The heat capacities of four samples of butyl methacrylate–methacrylic acid copolymers with 7.6 to 37.3 mol % acid are measured in the temperature range of 6 (80)–330 K. The thermodynamic characteristics (enthalpy, entropy, and Gibbs function) of the above copolymers are calculated. The isotherms of thermodynamic functions in the studied range of temperatures and copolymer compositions are plotted and analyzed. The ordering of the system (the entropy factor), rather than the energy of intermolecular interaction (the enthalpy factor), is found to make the main contribution to the change in the Gibbs function. BMA–MAA copolymer with 7.6 mol % acid is shown to be the best for use as a matrix for transdermal administration of drugs.