On the existence of a dynamic critical point by using wet milling on (±) modafinil

This study has been carried out on the molecular compound (±) modafinil, which exhibits five pure polymorphic forms (I, III, IV, V and VI). At P = 1 atm, irrespective of temperature and without any milling energy, Form I is the stable form. Therefore, the other polymorphic forms (III, IV, V and VI) are of monotropic character. The steady states of (±) modafinil have been investigated as a function of wet milling parameters (milling intensity and water concentration). The results presented here suggest the existence of a dynamic critical point defined by Tc ≈ 40°C, Pc ≈ 1 atm, Ic ≈ k R; R=50, Xc = 2% mass percent of water, respectively the critical: mean temperature, global pressure, milling intensity proportional to R and water composition (in mass percent).