The best way to calculate the thermodynamic properties of Polystyrene Sulfonate, (C8H7-SO3H), is to use a software called HSC Chemistry. This software has a comprehensive libraries of chemical compounds. All what you have to do is to enter the chemical reaction for formation of polystyrene sulfonate from its reactants hydrogen, water and SO3. The software will balance the equation for you and provide the thermodynamic properties such as the enthalpy of formation, Gibbs Free Energy of Formation and the Entropy for this reaction. You can get these thermodynamic properties at the room temperature or at any temperature that you specify.