Evolution equations for arbitrary moments of the orientation distribution of rigid-rod molecules

The kinetic theory for rigid-rod molecules has been successful in describin g a variety of experimental observations. from extremely dilute concentrati ons to the liquid crystalline limit. The theory is formulated in terms of a n orientation distribution function, whose tensorial moments can be related to measurable properties. We introduce here a general relation from which evolution equations for moments of arbitrary order can easily be derived. T he relation incorporates the effects of flow, magnetic and electric fields (permanent and induced dipoles), as well as "nematic" interactions necessar y to describe liquid crystalline transitions. Relevant features of the equa tion(s) with regard to possible closure strategies are briefly discussed. ( C) 1999 The Society of Rheology. [S0148-6055(99)01706-X].