A novel ionomer was successfully prepared by lactone ring opening of styrene-coumarin copolymer, containing 9.28 mol % of coumarin, with aqueous NaOH solution. Its solution properties in methanol, including reduced viscosity and surface tension, were investigated as a function of temperature, concentration, and pH value. The reduced viscosities of the ionomer solution decrease smoothly with increasing temperature and concentration. Moreover, the viscosities of the ionomer solution (0.3 g/dL, MeOH) are ca. twofold of the copolymer solution (0.3 g/dL THF) between 25 and 45 degrees C. It increases from ca. 0.14 to 0.59 dL/g as pH Value decreases from 10.6 to 6, then decreases slightly and reaches a constant value of 0.47 dL/g below pH 4.7. The surface tension of methanol solution decreases with increasing concentration and reaches an asymptotic value of 24.1 dyne/cm as the concentration is above 0.50 g/dL due to the surface-active effects. These properties can be related to the balance between hydrogen bonding and charge-charge interactions that occur along the ionomer backbone.